题目内容：

根据句意，用所给动词的正确形式填空。

1.You shouldn't keep the boy ________ (stand) outside.

2.They ______ (go) back in three years.

3.Great changes  _________(take) place since you left.

4.Let me see if it _________(rain) outside.

5._______ (walk) after meals is good for your health.

6.It's dangerous __________(swim) in the lake.

7.She never     (arrive)late, but she    (come) back at 10p.m. yesterday.

8.What     you     (do)at this time yesterday？