[A] New plants and animals then move into the area and begin to grow. [B] Just 2

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[A] New plants and animals then move into the area and begin to grow.

[B] Just 2 percent of the sunlight goes through the many layers of leaves and branches above, so understory plant species have developed special traits to cope with low light levels.

[C] On a smaller scale, large mammals, such as elephants, regularly destroy rain forest vegetation in the Congo River Basin in Africa.

[D] An understory of shorter trees and a lacework of woody vines, or lianas, produce a forest of such complex internal architecture that many animals, including some sizable ones, rarely or never descend to the ground.

[E] Less than one percent of the trees in the forest reside in the canopy and emergent layers.

[F] Because more light penetrates the canopy, however, the vegetation of the understory and forest floor is better developed than in the tropics.

[G] The rich, green canopy is teeming with life, and forest researchers have developed ingenious methods for accessing this mysterious ecosystem.

参考答案:

B本题考查的知识点是:段落内一致性原则+上下文的衔接本题空格出现在第一段中。上文提到热带雨林结构中的最低层是下层植被。下文提到,下层植被的植物叶子呈深红色,从而能够获取到达下层植被的少量的光。由此可见,上下文都围绕“下层植被”展开论述。出现关键词“understory”的选项有[B]、[D]和[F]。但是,[D]出现了上下文没有的新信息:“藤蔓植物”。[F]中出现了“冠层(canopy)”,但从下文即第一段倒数第二句对canopy一词的定义可知,它应在下文中第一次出现。由此排除[D]和[F]项。[B]强调