tìm n thuộc N* sao cho 1 * 2 * 3 * … * (n-1) chia hết cho n

Exercise 4:

1. I called Mr. Wilson at 9 last night but he was not at home. He was studying at the library.

2. I did not hear thunder during the storm last night because I was sleeping.

3. It was beautiful yesterday when we went for a walk in the park. The sun was shining and the birds were singing.

4. My brother and sister were talking about something when I walked into the room.

5. Tom went to his friend's house, but the boys were not there. They were playing soccer in the vacant lot down the street.

6. The little boy fell asleep while his mother was reading him a story.

7. I really enjoyed my holiday last January. While it was snowing in Iowa, the sun was shining in Florida.

8. While Ted was shoveling snow from his driveway yesterday, his wife brought him a cup of hot chocolate.

9. John had a car accident last week. He was driving down the street when suddenly a lorry hit his car from behind.

10. Ten years ago, the government decided to begin a food programme. At that time, many people in the rural areas were starving due to several years of drought.

11. They were waiting for me when I arrived at the station.

12. She was swimming in the sea when I saw her.

13. Were they playing tennis when it started raining?

14. We were driving home from the theatre when the police stopped us.

15. The wind was blowing very hard when I went out this morning.

Exercise 5:

1. went

2. was swimming

3. was drinking

4. saw

5. was

6. was beating

7. asked

8. told

9. stayed

10. ha