Mr Liu is ____ unusual teacher.He has written _____ useful book for his students.
— How do you improve your writing skills?—_________ .
I have spent______ on this job. I think I can finish it______this afternoon.
Boy, didn’t you see people were waiting in line? Don’t______in!
The weather is bad. You shouldn’t risk _______ mountains.
------Have you read the______ of the country you are going to?------Yes. Now I know it’s a country famous for natural beauty.