The destruction of habitats(栖息地)all over the world is the primar

The destruction of habitats(栖息地)all over the world is the primary reason species are?becoming extinct(灭绝)or endangered．Houses,highways,dams,industrial buildings,and?ever-spreading farms now dominate?21?formerly occupied by forests,deserts,and wetlands．22?the beginning of European settlement in America,23, over 65,000,000 acres of?wetlands have been drained．One million acres alone vanished 24?1985 and 1995． Habitat destruction can be?25?or it can be subtle,occurring over a 26?period of time?without being noticed．27?such as sewage from cities and chemical runoff fromfarms,can change?the?28?and quantity of water in streams and rivers．To?29?living in a delicately balanced?habitat,this disturbance can be as 30?as the clear-cutting of a rainforest． 31?remaining habitats are carved into smaller and smaller pockets or islands,remaining?species are forced to exist in these?32?areas,which causes further habitat?33?These?species become less adaptable to environmental?34；in fact,they become?35?endangered．Scientists believe that when a habitat is cut by 90%,one-half of its plants,animals and insects will?become extinct． 第31题的答案是（ ）
A、How
B、Whether
C、Before
D、As
【正确答案】：D
【题目解析】：第31题考查的是对句子结构和语境的理解。题目给出的句子是“31?remaining habitats are carved into smaller and smaller pockets or islands...”，这个句子描述的是随着栖息地被不断地分割成更小更小的区域或岛屿，剩余的物种被迫在这些有限的区域内生存，从而导致更多的栖息地丧失。 现在我们来分析四个选项： A. How - 这个词通常用来询问方式或方法，但在此句中，我们并不在询问栖息地被如何分割，因此A选项不合适。 B. Whether - 这个词用于引导一个表示选择或可能性的从句，但此句并没有提出需要选择或确定可能性的情况，所以B选项也不适用。 C. Before - 这个词用于表示在某个事件之前发生的情况，但在此句中，并没有提及任何需要在栖息地被分割之前发生的事件，所以C选项同样不适用。 D. As - 这个词在此处用作连词，表示随着某种情况的发生，另一种情况也随之发生。在这里，“as”引导的是一个状语从句，表示随着栖息地被不断分割成更小的区域，剩余物种的生存状况也受到了影响。这与句子的整体语境相符合。 综上所述，根据句子的结构和语境，第31题的正确答案应该是D选项，“As”。