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 from farms 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.
A. Landscapes B. cities C. maps D. pictures
Landscapes
cities
maps
pictures
空格后所说的森林、沙漠和湿地都是 陆地上的风景、风貌，这里是说森林、沙漠和湿地 都被房屋、公路、水坝、工业建筑、农场代替了。 landscapes有“风景”的意思，符合题意。cities意 为“城市”，maps意为“地图”，pictures意为“图画, 照片”。
A. At B. Before C. After D. Since
At
Before
After
Since
本句句意为：欧洲人开始在美国定居后，超过6500多万英亩的湿地变干。表示“在之 后”用after．故选C。
A. for example B. in addition C. at last D. after all
for example
in addition
at last
after all
前一句讲到湿地被房屋等替代，后一 句讲到欧洲殖民对湿地的破坏，这是对前一句的 举例说明。for example意为“例如”，符合题意。 in addition意为“此外”，at last意为“结果，终于”， after all意为“毕竟”。
A. both B. in C. between D. before
both
in
between
before
空格之后的两个年份之间有and，所 以前面要用between' between…and表示“在……之间”。
A. simple B. beneficial C. interesting D. obvious
simple
beneficial
interesting
obvious
本句承上启下，or之前的半句指前 文所说的短时间内的巨大变化，并且变化是明显 的。obvious意为“明显的”，符合题意。simple意 为“简单的”，beneficial意为“有益的”，interesting 意为“有趣的”。
A. long B. short C. happy D. sad
long
short
happy
sad
前文提到栖息地的破坏是明显的或者是微妙的，即可能很长时间其变化都没有被注意到。a．long period表示“很长一段时间”，故答案选A.
A. Construction B. Pollution C. Farming D. Living
Construction
Pollution
Farming
Living
城市污水和从田地流出来的化学药物都属于污染，pollution意为“污染”，符合题意，故选B。construction意为“建造”，farming意为“耕作”，living意为“生活”。
A. amount B. purity C. nature D. quality
amount
purity
nature
quality
此处意为：从城市和田地流出的污染 物改变了河水的质量和流量。quality and quantity 意为“质量和数量”，故选D。
A. people B. species C. plants D. insects
people
species
plants
insects
此处意为：对生存在这样处于微妙平 衡的环境中的物种来说，这样的干扰就像砍光雨 林一样致命。本句强调的是环境的改变对物种的 影响，前后文中也多次出现species，故选B。
A. effective B. species C. fatal D. surprising
effective
species
fatal
surprising
effective意为“有效的”，small意为 “小的”，fatal意为“致命的”，surprising意为“令人 吃惊的”。根据句意，故选C。
A. How B. Whether C. Before D. As
How
Whether
Before
As
剩余的栖息地被分割成越来越小的 区域或岛屿，与后文中物种生存在拥挤的地方是因果关系，所以要用引导原因状语的连词，as有 “由于，因为”的意思，故选D。
A. crowded B. extensive C. large D. bare
crowded
extensive
large
bare
栖息地越来越小，生存的空间也会变 得越来越拥挤，crowed意为“拥挤的”，符合题意。 extensive意为“广泛的”，large意为“大的”，bare 意为“荒芜的”。
A. reform B. destruction C. support D. discovery
reform
destruction
support
discovery
此处意为：物种被迫生活在拥挤的地 方，这会进一步导致栖息地的破坏。destruction意 为“破坏”，符合句意。reform意为“改革”，support 意为“支持”，discovery意为“发现”。
A. improvement B. changes C. protection D. development
improvement
changes
protection
development
此处意为：这些物种越来越不适应环 境的变化，这里是指栖息地被破坏后的变化。 change意为“变化”，符合语境。improvements意 为“改善”，protection意为“保护”，development意 为“发展”，都是指好的方向，不符合语境。
A. even B. far C. more D. less
even
far
more
less
环境越来越糟，使这些物种的处境更 加危险。more放在形容词前表示“更……”，故选C。