1. It is very useful to know english.

2. It has started snowing since 5 o'clock. 

3. Hung is shorter than Nam. 

4. What time did you go to bed last night? 

5. Do you know what time Nam goes to bed? 

6. It is good to do morning exercises. 

7. This book is as boring as that book.

8. Shall I have to sleep under a net? 

9. I haven't read that book since september $20^{th}$ 

10. An has been interested in healthy eating for 3 years ago. 

1. It is very useful to know English

2. It has snowed since 5 o'clock

3. Hung is shorter than Nam

4. What time did you go to bed last night?

5. Do you know when does Nam have to leave?

6. It's good to do morning exercise

7. This book is as boring as that one

8. Shall I have to sleep under a net?

9.  I haven't read a book since September 20th

10. An has been interested in healthy eating for 3 years