用所给词的适当形式填空。

1. ______ (help) us learn more about plants, we planted some seeds.

2. I'm sorry to keep you ______ (wait) for so long.

3. — Don't you forget ______ (meet) me 3 years ago here?

    — Sorry, I can't remember.

4. April 1st is April ______ (fool) Day.

5. Rose is ______ (pretty) girl in the school.

一只小船从甲地到乙地往返一次共用2小时，回来时顺水，比去时的速度每小时多行驶8千米，因此第二小时比第一小时多行驶6千米。那么甲、乙两地之间的距离是多少千米（）

A．15

B．16

C．24

D．30