1. Knowing English is very useful => It IS VERY USEFUL TO KNOW ENGLISH
2. It started to snow at 5 o'clock => It HAS STARTED SNOWING AT 5 O'CLOCK.
3.Nam is taller than Hung - HUNG IS SHORTER THAN NAM
4.When did you go to bed last night ? => What at timE DID YOU GO TO BED LAST NIGHT ?
5.What time does Nam have to leave ? => Do you know WHAT TIME NAM HAS TO LEAVE ?
6.To do morning exercises is good => It IS GOOD TO DO MORNING EXERCISES .
7.This book is very boring and so is that one => This book is as BORING AS THAT BOOK.
8. will it be necessary for me to sleep under a net ? => Shall I have to SLEEP UNDER A NET ?
9.. I last read a book on September 20th => I haven't READ THAT BOOK SINCE SEPTEMBER 20TH.
10. An began to be interested in healthy eating 3 years ago => An have been INTERESTED IN HEALTHY EATING FOR 3 YEARS.