Question

阅读下列短文，从每题所给的四个选项(A、B、C和D)中,选出最佳选项。

Big trees are incredibly important ecologically. For a start, they provide food for countless other species and shelter for many animals. With their tall branches in the sun, they capture vast amounts of energy. This allows them to produce massive crops of fruit and flowers that sustain much of the animal life in the forest.

Only a small number of tree species have the genetic ability to grow really big. The biggest are native to North America, but big trees grow all over the globe, from the tropics to the forests of the high latitudes(纬度). To achieve giant size, a tree needs three things: the right place to establish its seeding, good growing conditions and lots of time with low adult death rate. Lose any of these, and you will lose your biggest trees.

In some parts of the world, populations of big trees are dwindling because their seedings cannot survive. In southern India, for instance, an aggressive non-native bush, Lantana camara, is invading the floor of many forests. Lantana grows so thickly that young trees often fail to take root. With no young trees to replace them, it is only a matter of time before most of the big trees disappear.

Without the right growing conditions, trees cannot get really big and there is some evidence to suggest tree growth could slow in a warmer world, particularly in environments that are already warm. Having worked for decades at La Selva Biological Station in Puerto Viejo de Sarapiqui, Costa Rica, David and Deborah Clark and colleagues have shown that tree growth there declines markedly in warmer years. “During the day, their growth shuts down when it gets too warm, and at night they consume more energy because their metabolic(新陈代谢的)rate increases,” explains David Clark. With less energy produced in warmer years and more being consumed just to survive, there is even less energy available for growth.

The Clarks’ theory, if correct, means tropical forests would shrink over time. The largest, oldest trees would progressively die off and tend not to be replaced. According to the Clarks, this might cause a destabilization of the climate; as older trees die, forests would release some of their stored carbon into the atmosphere, causing a cycle of further warming, forest shrinkage and carbon emissions.

Besides, big trees face threats from elsewhere.

1. All the following factors are a must for making big trees EXCEPT_________.

A. genetic contribution

B. no deadly damage

C. ideal environment for growth

D. right place to establish its seeding

2.The word “dwindling”(paragraph3) is closest in meaning to “_______”.

A. exploding        B. decreasing

C. changing         D. growing

3. What is the best title of the passage?

A. Results of big trees’ disappearing.

B. Advantage of big trees.

C. Big trees in trouble

D. Importance of big trees to humans.

4.What will the author most probably discuss after the last paragraph?

A. Comparison between common trees and big ones.

B. The effect of human activities on big trees.

C. Benefits of big trees to the whole atmosphere.

D. More threats to the existence of big trees.

Answer

1.A

2.B

3.C

4.D

【解析】

试题分析：本文属于说明文，介绍了地球上的大树的重要作用，世界上的大树所面临的艰难现状，数量在不断减少，分析了这一情况出现的原因。

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【名师点睛】

本文5.

要想解决好主旨大意题，首先要找到主题句或中心句，就可以依据主题句或中心句归纳主题。在做此类阅读理解题时，考生要特别注意：

1．首段陷阱。即首段虽然貌似主题句或中心句，但却没有完整概括文章全意，或只片面地说到文章的某一个层次，或者是作者设置的几个需要读者判定的文意。这样的信息用来做主题句或中心句就会落入陷阱。

2. 以偏概全：这就是说此类题型的选项中往往出现这些干扰项目：

⑴．局部信息，即选项的内容小于文章的内容。考生认为此选项有含中心句的成分，就认为可以作为中心句，就犯了以点概面、以偏概全的错误。

⑵．范围过宽，即选项的内容大于文章的内容。考生认为中心句的内容全涵盖在此选项里，就认为此选项正确，就犯了外延大而内涵小的错误。

3. 过于笼统。即选项中归纳的主题太泛，与细节脱节或是没有对细节加以充分论证。这样的选项貌似与主题句接近，实则经不起推敲，不应该扰乱考生的判断。

4. 把观点强加给作者。考生往往根据自己对文章的判断而选择了与自己观点相接近的选项，而忽视了文章中客观的作者见解。

考点：考查说明文阅读