一、

1．are swimming

2．are running

3．are practicing

4．was, doing

5．were listening

6．were reading

7．were watching

8．was making

二、

1．Is he dancing?

2．The farmers were working last year．

3．What are the teachers doing?

4．What are the boys doing?

5．The singer isn't singing any famous songs．

6．I'm not studying English, either．

三、

1．I am writing a letter to my friend in Beijing．

2．What were you doing at that time?

3．I was watching TV when you called me last night．