I/

1. I'm not sure what's wrong with the car. It didn't happen before.

2.My brother and I went swimming when we were small.

3. Mrs. Nhung finished housework. She is going to sleep.

4. Everyone believes that you are the smartest student in the class.

5. Who Made That Horrible Noise? - It's Nam. He practices guitar.

6.The park gate locks at 6:30 p.m every night.

7. Not only children but their father also likes watching cartoons in his spare time.

8.i regret inform you that the train was canceled

9. Mrs. Hoa used gets up early to prepare breakfast for her family.

II/

1. Can you tell me what you have done last night?->did

2. What do you do if you see someone throw trash on the street?->saw; throwing

3. Tom wants to go abroad and he doesn't have enough money.->but

4. The meeting will be held at 9am to 10am tomorrow.->from

5. Most ants can lift objects ten heavier than own body ->bodies

6. I suggested Hoa to takes part  in the English Speech Contest.->suggest

7. That big ship carried a lot of men, women and children.->  Was carrying

8. I haven't been to New York before and either has my sister.->have never; also have

9. What a lovely day us had!->for us

10. I prefer listening to music to watching TV in my free time.->than