A large fish was slowly swimming through the water, its tail _

单选题 A large fish was slowly swimming through the water, its tail __ back and forth like the pendulum of a clock．

A．swung
B．was swinging
C．was swung
D．swinging

参考答案D

解析: D。一条大鱼在水里慢慢游过，尾巴像钟摆一样来回摆动。
考查非谓语动词。逗号之前为主句，具备完整的主谓结构；逗号后没有连词，但是有主语，因此应该是一个独立主格结构；swing为不及物动词，和tail间为主动关系，所以使用现在分词。

单选题 They are teachers and don't realize __ to start and run a company．

A．what it takes
B．what takes it
C．what they take
D．what takes them

单选题 The millions of calculations involved, __ by hand, would have lost all practical value by the time they were finished．

A． had they been done
B．having been done
C．they had been done
D．they were done

单选题 When you have finished that book, don't forget to put it on the bookshelf, ．__ ?

A．do you
B．will you
C．don't you
D．won't you