Bài tập 1: Chọn đúng thì của các câu sau:
1. I saw/ was seeing the accident when I was waiting for the taxi.
2. What were you doing/ did you do when I phoned?
3. They didn't visit/ weren't visiting their friends last summer holiday.
4. It rained/ was raining heavily last July.
5. While people were talking to each other, he read/ was reading his book.
6. Chris was eating/ ate pizza every weekend last month.
7. While we were running/ run in the park, Mary fell over.
8. Did you find/ Were you finding your keys yesterday?
9. Who was she dancing/ did she dance with at the party last night?
10. They were watching/ watched football on TV all day.