The girl is very smart, but I don’t think the maths problem is _________ for her __________?
---Excuse me, sir. Could you please tell me _______? --- Sorry, I don’t know. You can go to the information desk.
---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.