生物的各个物种既基本上保持稳定，又能不断地进化，原因是生物具

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问题选择题

生物的各个物种既基本上保持稳定，又能不断地进化，原因是生物具有[ ]

A．新陈代谢作用

B．遗传和变异的特性

C．生命的物质和结构基础

D．生殖和发育的现象

答案

答案：B

填空题

用所给单词的适当形式填空。

1. Look, the girls ______________ (sing) now.

2. Peter ______________ (want) ______________ (write) a letter to his friend.

3. Would you like ______________ (join) ______________ (we)?

4. There is a lot of ______________ (rain) here.

5. What ______________ (do) she usually do? She usually ______________ (catch) insects.

6. They ______________ (have) a picnic this weekend.

7. I like ______________ (swim) very much.

问答题论述题

论述连铸坯热装热送的意义。