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.
