南亚是人口分布密集的地区，其中人口数量超过一亿的国家共有（ _爱下问搜题

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问题选择题

南亚是人口分布密集的地区，其中人口数量超过一亿的国家共有（　　）

A．1个

B．2个

C．3个

D．4个

答案

答案：C

判断题

小半径曲线上铺设的无缝线路，因为胀轨跑道比断轨具有更大的危险性，所以应适当提高长轨的锁定轨温。

单项选择题

Since life began eons ago, thousands of creatures have come and gone. Some, such as the dinosaurs, became extinct due to naturally changing ecologic conditions. More recent threats to life forms are humans and their activities. Man has drained marshes, burned prairies, dammed and diverted rivers. Some of the more recent casualties of man’s expansion have been the dodo, great auk, passenger pigeon, Irish elk, and Steller’s sea cow. Sadly, we can no longer attribute the increasing decline in our wild animals and plant species to "natural" processes. Many species are dying out because of exploitation, habitat alteration or destruction, pollution, or the introduction of new species of plants and animals to an area. As mandated by Congress, protecting endangered species, and restoring them to the point where their existence is no longer jeopardized, is the primary objective of the U.S. Fish and Wilidlife Service’s Endangered Species Program.

Which of the following has become extinct due to man’s destruction

A．African elephant

B．Irish elk

C．Giant panda

D．White Bengal