1. Alice saw/ was seeing the accident when she was catching the bus.

2. What were you doing/ did you do when I called?  (dấu hiệu nhận biết: "called")

3. I didn't visit/weren't visiting my friends last summer holiday. (dấu hiệu nhận biết : "last summer holiday")

4. It rained/was raining heavily last July. (dấu hiệu nhận biết: "last July")
5. While people were talking to each other, he read/ was reading his book.
6. My sister was eating/ ate hamburgers every weekend last month. (dấu hiệu nhận biết: "last month")
7. While we were running/ ran in the park, Mary fell over.
8. Did you find/ Were you finding your keys yesterday? (dấu hiệu nhận biết: "yesterday")
9. Who was she dancing/ did she dance with at the party last night? (dấu hiệu nhận biết: "last night")
10. They were watching/watched football on TV at 7 p.m. yesterday.  (dấu hiệu nhận biết: "yesterday")

1. saw (hành động xen ngang )

2. were you doing ( hành động gọi xen ngang )

3. didn’t visit 

4. rained 

5. was reading ( 2 hành động  xảy ra song song )

6. ate 

7.were running

8. Did you find 

9. did she dance 

10. watched