This is one of the best films _________ this year.

You look unhappy, what’s happening, my son? —I’m wondering how long it’ll be________ we come to China again.

He__________ he would be able to leave tomorrow, but it’s beginning to took difficult.

Some people fear that ______ air pollution may bring about changes in ______ weather around the world.

Let’s go hiking ______ staying at home, shall we? — A good idea. [ ]