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 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.31._____.
A、How
B、Whether
C、Before
D、As
【正确答案】：D
【题目解析】：理解判断题。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。