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27题的答案是（ ）
A、Construction
B、Pollution
C、Farming
D、Living
【正确答案】：B
【题目解析】：第27题考察的是对上下文的理解和词汇的匹配。根据句子“27?such as sewage from cities and chemical runoff from farms, can change the?28?and quantity of water in streams and rivers.”可以推断出，此处描述的是某种能够改变河流和溪流水质和数量的因素。选项中，只有“Pollution”（污染）能够符合这种描述。因为城市的污水和农场的化学径流都是环境污染的源头，它们能够改变水体的生态平衡，对栖息地的破坏具有显著影响。 因此，答案是B，“Pollution”（污染）。