問題詳情

Redwood trees are the tallest plants on the earth, reaching heights of up to 100 meters. They are also known for their longevity, typically 500 to 1000 years, but sometimes more than 2000 years. A hundred million years ago, in the age of dinosaurs, redwoods were common in the forests of a much more moist and tropical North America. As the climate became drier and colder, they retreated to a narrow strip along the Pacific coast of Northern California.The trunk of redwood trees is very stout and usually forms a single straight column. It is covered with a beautiful soft, spongy bark. This bark can be pretty thick, well over two feet in the more mature trees. It gives the older trees a certain kind of protection from insects, but the main benefit is that it keeps the center of the tree intact from moderate forest fires because of its thickness. This fire resistant quality explains why the giant redwood grows to live that long. While most other types of trees are destroyed by forest fires, the giant redwood actually prospers because of them. Moderate fires will clear the ground of competing plant life, and the rising heat dries and opens the ripe cones of the redwood, releasing many thousands of seeds onto the ground below.New trees are often produced from sprouts, little baby trees, which form at the base of the trunk. These sprouts grow slowly, nourished by the root system of the “mother” tree. When the main tree dies, the sprouts are then free to grow as full trees, forming a “fairy ring” of trees around the initial tree. These trees, in turn, may give rise to more sprouts, and the cycle continues.
53. Why were redwood trees more prominent in the forests of North America millions of years ago?
(A) The trees were taller and stronger.
(B) The soil was softer for seeds to sprout.
(C) The climate was warmer and more humid.
(D) The temperature was lower along the Pacific coast.

參考答案

答案：C
難度：適中0.470588
統計：A(1),B(4),C(8),D(4),E(0)

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