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.What time does Nam have to leave?
---->Do you know what time nam has to leave
4.To do morning exercises is good
---->It is good to do morning exercises
5. This book is very boring and so is that one
--->This book is as boring at that book
6.Will it be necessary for me to sleep under a net
--->Shall i have to sleep under a net
7.I last read a book on September 20th
--->T haven't read that book since september 20th
8. An began to be interested in healthy eating 3 years ago
----> An has been interested in healthy eating for 3 years