问题 单项选择题

一阶线性非齐次方程求解公式推导的方法是()。

A.特征根法

B.常数变异法

C.变量变换法

D.积分因子法

答案

参考答案:B

完形填空

阅读短文,用括号内单词的适当形式填空。

Last Sunday the elephant keeper at London Zoo, Jim Robson,   小题1:  (kill) by one of the elephants he loved. This was terrible, and it could be a big problem for the future of London Zoo—and maybe for all of Britain’s city zoos.

London Zoo said that it   小题2:  (move) its three elephants to a wild animal park outside London. Its director-general(总经理), Michael Dixon, said, “We are sorry that the elephants   小题3: (leave); there   小题4:   (be) elephants at London Zoo since 1831.”

One British newspaper said that though many small animals were very interesting, most people wanted to see big animals—and most of all elephants.

London Zoo is not only losing its elephants. The tigers will also leave soon and most of the bears have already gone. Outside the elephant house at London Zoo, a woman   小题5:  (call) Mary said she wished the zoo  小题6:  (keep) big animals. “This is the only way the young people can see animals without  小题7:  (travel) to other countries,” she said.

Zoos are not very good places for animals, but they can help to well keep them. Children can also learn a lot about the animals when they visit zoos.

Another visitor, a man called Alan, was very angry. “If the elephants  小题8: (send) back to the wild, they will die. If you take away big animals, people will stop  小题9: (visit) London Zoo. It can survive (继续生存)at the moment, but it   小题10:  (not survive) in the future. "

However, Mary Rosevear, director of the Federation of Zoos, believes that city zoos can survive without keeping large animals.

单项选择题