16, He ask Lan How many students there were in the college.

17, Lan asked me who was the headmaster.

18, He asked Nga what country she came from.

19, Lan asked me how long I stayed there.

20, He asked Lan how she would use English in the future.

Ex3:

1, He said he was there 2 days before.

2, She asked me where I went the previous night.

3, They told him they would visit Ha Long Bay the following week.

4, Tuan asked me whether I liked classical music.

5, I wondered if the package would arrive on time.

6, Hoa asked me which place in Viet Nam I would spend in my summer vacation.

7, she says her brother wants to be a pilot. ( cấu trúc này có say nên động từ giữ nguyên)

8, The police warned that no entertainment activities will behold during the typhoon. ( câu này mình ko chắc lắm)