Key:
1. D 2. A 3. B 4. C 5. C 6. B 7. B 8. A 9. C 10. D 11. C 12. D 13. 2 4 6
題目解析：
1. The word “dramatic” in the passage is closest in meaning to （Vocabulary Question）
A.Gradual
B.Complex
C.Visible
D.Striking
相關原句：
The transition from forest to treeless tundra on a mountain slope is often a dramatic one.（Paragraph 1）
本題解析：
dramatic意為“戲劇化的，驚人的”，與striking同義，因此選擇D。
正確答案：D
2. Where is the lower timberline mentioned in paragraph 1 likely to be found?（Factual Information Question）
A.In an area that has little water
B.In an area that has little sunlight
C.Above a transition area
D.On a mountain that has on upper timberline.
相關原句：
In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge…（Paragraph 1）
本題解析：
在本干旱地區(qū)樹帶界線1較低，即水分較少的地區(qū)會有較低的樹帶界線1，因此選擇A。
正確答案：A
3. Which of the following can be inferred from paragraph 1 about both the upper and lower timberlines?（Inference Question）
A.Both are treeless zones
B.Both mark forest boundaries.
C.Both are surrounded by desert areas.
D.Both suffer form a lack of moisture.
相關原句：
Within a vertical distance of just a few tens of meters, trees disappear as a life-form and are replaced by low shrubs, herbs, and grasses. This rapid zone of transition is called the upper timberline or tree line. （Paragraph 1）
In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture. （Paragraph 1）
本題解析：
無論是upper timberline還是lower timberline，它們都是樹木消失的界線1，因此選擇B。
正確答案：B
4. Paragraph 2 supports which of the following statements about deciduous trees?（Factual Information Question）
A.They cannot grow in cold climates.
B.They do not exist at the upper timberline.
C.They are less likely than evergreens to survive at the upper timberline.
D.They do not require as much moisture as evergreens do.
相關原句：
Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline.（Paragraph 2）
本題解析：
常青樹比落葉樹更能適應極線1的生存環(huán)境，更容易存活（have some advantage over deciduous trees (those that lose their leaves) in the extreme environments），因此選擇C。注意文中亦指出在喜馬拉雅山部分地區(qū)的樹帶界線1處有落葉樹，B錯誤。
正確答案：C
5. The word attain in the passage is closest in meaning to（Vocabulary Question）
A.require
B.resist
C.achieve
D.endure
相關原句：
This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges…（Paragraph 3）
本題解析：
attain意為“獲得，得到”，此處指樹木可以達到某一高度，即achieve，因此選擇C。
正確答案：C
6. The word they in the passage refers to （Reference Question）
A.valleys
B.trees
C.heights
D.ridges
相關原句：
As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there. （Paragraph 3）
本題解析：
即樹木在山脊處長得更高，雖然在那里它們要經(jīng)受更多考驗，they指代trees，因此選擇B。
正確答案：B
7. The word prone in the passage is closest in meaning to（Vocabulary Question）
A.adapted
B.likely
C.difficult
D.resistant
相關原句：
In the tropics, the valleys appear to be more favorable because they are less prone to dry out, they have less frost, and they have deeper soils. （Paragraph 3）
本題解析：
prone意為“有…傾向”，即“容易變得…，很可能…（likely）”，因此選擇B。
正確答案：B
8. According to paragraph 3, which of the following is true of trees in the middle and upperlatitudes?
（Factual Information Question）
A.Tree growth is negatively affected by the snow cover in valleys.
B.Tree growth is greater in valleys than on ridges.
C.Tree growth on ridges is not affected by high-velocity winds.
D.Tree growth lasts longer in those latitudes than it does in the tropics.
相關原句：
This is because middle- and upper- latitude timberlines are strongly influenced by the duration and depth of the snow cover. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there. （Paragraph 3）
本題解析：
文中指出中高緯度的樹木之所以在山脊處長的更高是因為山谷處的積雪太深太久，對其生長不利，所以即使山脊環(huán)境有諸多不利（風大，土壤貧瘠等），樹木還是在山脊長得更高。因此選擇A。
正確答案：A
9. Which of the sentences below best express the essential information in the highlighted sentence in the passage? （Sentence Simplification Question）
A.Because of their deformed shapes at high altitudes, trees are not likely to be seriously harmed by the strong winds typical of those altitudes.
B.As altitude increases, the velocity of winds increase, leading to a serious decrease in the number of trees found at high altitudes.
C.The deformed shapes of trees at high altitudes show that wind velocity, which increase with altitude, can cause serious hardship for trees.
D.Increased wind velocity at high altitudes deforms the shapes of trees, and this may cause serious stress for trees.
相關原句：
Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes.（Paragraph 4，highlighted sentence）
本題解析：
風速隨著海拔升高而提升，并可能給樹造成嚴重的壓力，正如高海拔地區(qū)樹木變形已經(jīng)證明了這一點。也就是說樹木變形說明了高速風對植物產生的嚴重壓力（cause serious stress for trees），因此選擇C。注意，D錯誤之處在于并不是變形給樹造成壓力，而是高速風給樹造成了壓力，變形只是壓力的表現(xiàn)。
正確答案：C
10. In paragraph 4, what is the author’s main purpose in the discussion of the dramatic cessation of tree growth at the upper timberline?
（Rhetorical Purpose Question）
A.To argue that none of several environment factors that are believed to contribute to that phenomenon do in fact play a role in causing it.
B.To argue in support of one particular explanation of that phenomenon against several competing explanations.
C.To explain why the primary environmental factor responsible for that phenomenon has not yet been identified.
D.To present several environmental factors that may contribute to a satisfactory explanation of that phenomenon.
相關原句：
There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role.（Paragraph 4）
本題解析：
作者提到樹帶界線1處樹木的消失很驚人，是為下文講述出現(xiàn)這一現(xiàn)象的原因(environmental factors)做鋪墊，因此選擇D。
正確答案：D
11. According to paragraph 6, all of the following statements are true of plants in the alpine zone EXCEPT:（Negative Factual Information Question）
A.Because they are low, they are less exposed to strong winds.
B.Because they are low, the winter snow cover gives them more protection from the extreme cold.
C.In the equatorial mountains, they tend to be lower than in mountains elsewhere.
D.Their low growth form keeps them closer to the ground, where there is more heat than further up.
相關原句：
This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface.（Paragraph 6）
The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. （Paragraph 6）
In the equatorial mountains the low growth form is less prevalent.（Paragraph 6）
本題解析：
文章指出在熱帶地區(qū)的山上（equatorial mountains），低矮生長形態(tài)便不多見了（less prevalent），C選項卻稱在熱帶地區(qū)植物更低矮，錯誤，因此選擇C。ABD選項內容文中都有提及。
正確答案：C
12. Look at the four squares [ █ ] that indicate where the following sentence could be added to the passage.
（Insert Text Question）
This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.
Where would the sentence best fit? Click on a square to add the sentence to the passage.
Above the tree line there is a zone that is generally called alpine tundra. █(A)Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants.█(B) Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas.█(C) At this great height, rocks, warmed by the sun, melt small snowdrifts.█(D) This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.
本題解析：
插入句中“this explains”和“6180 meters”與前句中“around 6100 meters”和“rocks, warmed by the sun, melt small snowdrifts（植物能存活的原因）”相呼應，插入句作為例子（for example）進一步說明了為何在高緯度植物能夠存活。因此選擇D。
正確答案：D
13. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
（Prose Summary Question）
At the timberline, whether upper or lower, there is a profound change in the growth of trees and other plants.
●
●
●
Answer choices
1.Birch is one of the few species of tree that can survive in the extreme environments of the upper timberline.
2.There is no agreement among scientists as to exactly why plant growth is sharply different above and below the upper timberline.
3.The temperature at the upper timberline is probably more important in preventing tree growth than factors such as the amount of snowfall or the force of winds.
4.The geographical location of an upper timberline has an impact on both the types of trees found there and their physical characteristics.
5.High levels of ultraviolet light most likely play a greater role in determining tree growth at the upper timberline than do grazing animals such as the ibex.
6.Despite being adjacent to the timberline, the alpine tundra is an area where certain kinds of low trees can endure high winds and very low temperatures.
本題解析：
1.文中提到birch是為了說明有些闊葉樹也可以在上樹帶界線1生長，而不是說birch是少數(shù)的能在極線1生態(tài)環(huán)境下生長的植物（“There are some areas, however, where broadleaf deciduous trees form the timberline. Species of birch, for example, may occur at the timberline in parts of the Himalayas.”第二段）。1錯誤。
2. “Various environmental factors may play a role”，“Some scientists have proposed that …”都說明對于樹帶界線1處植被極端變化的原因是猜測出來的。2正確。
3.該選項迷惑性較大。需注意選項所指的是“in preventing tree growth”，氣溫并不是阻止植物生長，而是“for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months”，即氣溫太冷加上植物不夠成熟導致植物凍死。3錯誤。
4. “At the upper timberline the trees begin to become twisted and deformed. This is particularly true for trees in the middle and upper latitudes…”與“Timberline trees are normally evergreens,There are some areas, however, where broadleaf deciduous trees form the timberline…”來自于二、三兩段，該兩段都說明地理位置不同，樹帶界線1處的樹木種類和形態(tài)都不同。4正確。
5.文中只說明紫外線強度和放牧可能是導致樹帶界線1處樹木消失的原因，但并未指出哪一原因作用更大。5錯誤。
6.“The most striking characteristic of the plants of the alpine zone is their low growth form. This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface”來自第
六段，該段說明了苔原環(huán)境下低矮植物能夠承受惡劣環(huán)境。6正確。
正確答案：2，4，6
1. D 2. A 3. B 4. C 5. C 6. B 7. B 8. A 9. C 10. D 11. C 12. D 13. 2 4 6
題目解析：
1. The word “dramatic” in the passage is closest in meaning to （Vocabulary Question）
A.Gradual
B.Complex
C.Visible
D.Striking
相關原句：
The transition from forest to treeless tundra on a mountain slope is often a dramatic one.（Paragraph 1）
本題解析：
dramatic意為“戲劇化的，驚人的”，與striking同義，因此選擇D。
正確答案：D
2. Where is the lower timberline mentioned in paragraph 1 likely to be found?（Factual Information Question）
A.In an area that has little water
B.In an area that has little sunlight
C.Above a transition area
D.On a mountain that has on upper timberline.
相關原句：
In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge…（Paragraph 1）
本題解析：
在本干旱地區(qū)樹帶界線1較低，即水分較少的地區(qū)會有較低的樹帶界線1，因此選擇A。
正確答案：A
3. Which of the following can be inferred from paragraph 1 about both the upper and lower timberlines?（Inference Question）
A.Both are treeless zones
B.Both mark forest boundaries.
C.Both are surrounded by desert areas.
D.Both suffer form a lack of moisture.
相關原句：
Within a vertical distance of just a few tens of meters, trees disappear as a life-form and are replaced by low shrubs, herbs, and grasses. This rapid zone of transition is called the upper timberline or tree line. （Paragraph 1）
In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture. （Paragraph 1）
本題解析：
無論是upper timberline還是lower timberline，它們都是樹木消失的界線1，因此選擇B。
正確答案：B
4. Paragraph 2 supports which of the following statements about deciduous trees?（Factual Information Question）
A.They cannot grow in cold climates.
B.They do not exist at the upper timberline.
C.They are less likely than evergreens to survive at the upper timberline.
D.They do not require as much moisture as evergreens do.
相關原句：
Timberline trees are normally evergreens, suggesting that these have some advantage over deciduous trees (those that lose their leaves) in the extreme environments of the upper timberline.（Paragraph 2）
本題解析：
常青樹比落葉樹更能適應極線1的生存環(huán)境，更容易存活（have some advantage over deciduous trees (those that lose their leaves) in the extreme environments），因此選擇C。注意文中亦指出在喜馬拉雅山部分地區(qū)的樹帶界線1處有落葉樹，B錯誤。
正確答案：C
5. The word attain in the passage is closest in meaning to（Vocabulary Question）
A.require
B.resist
C.achieve
D.endure
相關原句：
This is particularly true for trees in the middle and upper latitudes, which tend to attain greater heights on ridges…（Paragraph 3）
本題解析：
attain意為“獲得，得到”，此處指樹木可以達到某一高度，即achieve，因此選擇C。
正確答案：C
6. The word they in the passage refers to （Reference Question）
A.valleys
B.trees
C.heights
D.ridges
相關原句：
As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there. （Paragraph 3）
本題解析：
即樹木在山脊處長得更高，雖然在那里它們要經(jīng)受更多考驗，they指代trees，因此選擇B。
正確答案：B
7. The word prone in the passage is closest in meaning to（Vocabulary Question）
A.adapted
B.likely
C.difficult
D.resistant
相關原句：
In the tropics, the valleys appear to be more favorable because they are less prone to dry out, they have less frost, and they have deeper soils. （Paragraph 3）
本題解析：
prone意為“有…傾向”，即“容易變得…，很可能…（likely）”，因此選擇B。
正確答案：B
8. According to paragraph 3, which of the following is true of trees in the middle and upperlatitudes?
（Factual Information Question）
A.Tree growth is negatively affected by the snow cover in valleys.
B.Tree growth is greater in valleys than on ridges.
C.Tree growth on ridges is not affected by high-velocity winds.
D.Tree growth lasts longer in those latitudes than it does in the tropics.
相關原句：
This is because middle- and upper- latitude timberlines are strongly influenced by the duration and depth of the snow cover. As the snow is deeper and lasts longer in the valleys, trees tend to attain greater heights on the ridges, even though they are more exposed to high-velocity winds and poor, thin soils there. （Paragraph 3）
本題解析：
文中指出中高緯度的樹木之所以在山脊處長的更高是因為山谷處的積雪太深太久，對其生長不利，所以即使山脊環(huán)境有諸多不利（風大，土壤貧瘠等），樹木還是在山脊長得更高。因此選擇A。
正確答案：A
9. Which of the sentences below best express the essential information in the highlighted sentence in the passage? （Sentence Simplification Question）
A.Because of their deformed shapes at high altitudes, trees are not likely to be seriously harmed by the strong winds typical of those altitudes.
B.As altitude increases, the velocity of winds increase, leading to a serious decrease in the number of trees found at high altitudes.
C.The deformed shapes of trees at high altitudes show that wind velocity, which increase with altitude, can cause serious hardship for trees.
D.Increased wind velocity at high altitudes deforms the shapes of trees, and this may cause serious stress for trees.
相關原句：
Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes.（Paragraph 4，highlighted sentence）
本題解析：
風速隨著海拔升高而提升，并可能給樹造成嚴重的壓力，正如高海拔地區(qū)樹木變形已經(jīng)證明了這一點。也就是說樹木變形說明了高速風對植物產生的嚴重壓力（cause serious stress for trees），因此選擇C。注意，D錯誤之處在于并不是變形給樹造成壓力，而是高速風給樹造成了壓力，變形只是壓力的表現(xiàn)。
正確答案：C
10. In paragraph 4, what is the author’s main purpose in the discussion of the dramatic cessation of tree growth at the upper timberline?
（Rhetorical Purpose Question）
A.To argue that none of several environment factors that are believed to contribute to that phenomenon do in fact play a role in causing it.
B.To argue in support of one particular explanation of that phenomenon against several competing explanations.
C.To explain why the primary environmental factor responsible for that phenomenon has not yet been identified.
D.To present several environmental factors that may contribute to a satisfactory explanation of that phenomenon.
相關原句：
There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role.（Paragraph 4）
本題解析：
作者提到樹帶界線1處樹木的消失很驚人，是為下文講述出現(xiàn)這一現(xiàn)象的原因(environmental factors)做鋪墊，因此選擇D。
正確答案：D
11. According to paragraph 6, all of the following statements are true of plants in the alpine zone EXCEPT:（Negative Factual Information Question）
A.Because they are low, they are less exposed to strong winds.
B.Because they are low, the winter snow cover gives them more protection from the extreme cold.
C.In the equatorial mountains, they tend to be lower than in mountains elsewhere.
D.Their low growth form keeps them closer to the ground, where there is more heat than further up.
相關原句：
This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface.（Paragraph 6）
The low growth form can also permit the plants to take advantage of the insulation provided by a winter snow cover. （Paragraph 6）
In the equatorial mountains the low growth form is less prevalent.（Paragraph 6）
本題解析：
文章指出在熱帶地區(qū)的山上（equatorial mountains），低矮生長形態(tài)便不多見了（less prevalent），C選項卻稱在熱帶地區(qū)植物更低矮，錯誤，因此選擇C。ABD選項內容文中都有提及。
正確答案：C
12. Look at the four squares [ █ ] that indicate where the following sentence could be added to the passage.
（Insert Text Question）
This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.
Where would the sentence best fit? Click on a square to add the sentence to the passage.
Above the tree line there is a zone that is generally called alpine tundra. █(A)Immediately adjacent to the timberline, the tundra consists of a fairly complete cover of low-lying shrubs, herbs, and grasses, while higher up the number and diversity of species decrease until there is much bare ground with occasional mosses and lichens and some prostrate cushion plants.█(B) Some plants can even survive in favorable microhabitats above the snow line. The highest plants in the world occur at around 6,100 meters on Makalu in the Himalayas.█(C) At this great height, rocks, warmed by the sun, melt small snowdrifts.█(D) This explains how, for example, alpine cushion plants have been found growing at an altitude of 6,180 meters.
本題解析：
插入句中“this explains”和“6180 meters”與前句中“around 6100 meters”和“rocks, warmed by the sun, melt small snowdrifts（植物能存活的原因）”相呼應，插入句作為例子（for example）進一步說明了為何在高緯度植物能夠存活。因此選擇D。
正確答案：D
13. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
（Prose Summary Question）
At the timberline, whether upper or lower, there is a profound change in the growth of trees and other plants.
●
●
●
Answer choices
1.Birch is one of the few species of tree that can survive in the extreme environments of the upper timberline.
2.There is no agreement among scientists as to exactly why plant growth is sharply different above and below the upper timberline.
3.The temperature at the upper timberline is probably more important in preventing tree growth than factors such as the amount of snowfall or the force of winds.
4.The geographical location of an upper timberline has an impact on both the types of trees found there and their physical characteristics.
5.High levels of ultraviolet light most likely play a greater role in determining tree growth at the upper timberline than do grazing animals such as the ibex.
6.Despite being adjacent to the timberline, the alpine tundra is an area where certain kinds of low trees can endure high winds and very low temperatures.
本題解析：
1.文中提到birch是為了說明有些闊葉樹也可以在上樹帶界線1生長，而不是說birch是少數(shù)的能在極線1生態(tài)環(huán)境下生長的植物（“There are some areas, however, where broadleaf deciduous trees form the timberline. Species of birch, for example, may occur at the timberline in parts of the Himalayas.”第二段）。1錯誤。
2. “Various environmental factors may play a role”，“Some scientists have proposed that …”都說明對于樹帶界線1處植被極端變化的原因是猜測出來的。2正確。
3.該選項迷惑性較大。需注意選項所指的是“in preventing tree growth”，氣溫并不是阻止植物生長，而是“for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months”，即氣溫太冷加上植物不夠成熟導致植物凍死。3錯誤。
4. “At the upper timberline the trees begin to become twisted and deformed. This is particularly true for trees in the middle and upper latitudes…”與“Timberline trees are normally evergreens,There are some areas, however, where broadleaf deciduous trees form the timberline…”來自于二、三兩段，該兩段都說明地理位置不同，樹帶界線1處的樹木種類和形態(tài)都不同。4正確。
5.文中只說明紫外線強度和放牧可能是導致樹帶界線1處樹木消失的原因，但并未指出哪一原因作用更大。5錯誤。
6.“The most striking characteristic of the plants of the alpine zone is their low growth form. This enables them to avoid the worst rigors of high winds and permits them to make use of the higher temperatures immediately adjacent to the ground surface”來自第
六段，該段說明了苔原環(huán)境下低矮植物能夠承受惡劣環(huán)境。6正確。
正確答案：2，4，6
