--Listen! Tom is singing in the next room.--It _______ be Tom. He has gone to Shanghai.
---Jim, can you finish your homework on time? ---______. I can finish it.
We are sure to enter a better high school ________ we work hard.
We must protect water from being _________, because it’s the source of life.
My father ______ in China for 20 years already. He thinks his job is great.
______ good advice the teacher gave me!