2. 专升本
  3. Trees have a spectacular (壮丽的；奇观的) survival record. Over a period of more than 400 million years, they have evolved as the talle

Trees have a spectacular (壮丽的；奇观的) survival record. Over a period of more than 400 million years, they have evolved as the talle

admin2007-12-30  57
问题     Trees have a spectacular (壮丽的；奇观的) survival record. Over a period of more than 400 million years, they have evolved as the tallest, most massive, and longest-lived organisms ever to inhabit the Earth. Yet trees lack a means of defense that almost every animal has: trees cannot move away from destructive forces. Because they cannot move, all types of living and nonliving enemies—fire, storms, microorganisms, insects, other animals and, later, humans—have wounded them throughout their history. Trees have survived because their evolution has made them into highly compartmented (分隔的) organisms: that is, they wall off injured and infected wood.
    In that respect trees are radically different from animals. Fundamentally, animals heal, they preserve their life by making billions of repair, installing (安置) new cells or rejuvenated (恢复活力的) cells in the positions of old ones. Trees cannot heal; they make no repairs. Instead, they defend themselves from the consequences of injury and infection by walling off the damage. At the same time they put new cells in new positions; in effect, they grow a new tree over the old one every year. The most obvious results of the process are growth rings, which are visible on the cross section of a trunk, a root, or a branch.
The author’s main purpose in this article is to explain the______.
选项 A、life cycle of a tree
B、way trees survive
C、importance of trees to human progress
D、dangers trees face from natural disasters
答案B
解析
转载请注明原文地址:https://jikaoti.com/ti/B6JGFFFM
本试题收录于： 英语题库普高专升本分类
0

英语

普高专升本

相关试题推荐
随机试题
最新回复(0)