Since Tom ___downloaded a virus into his computer, he can not open the file now.
He missed _______ when he was in Africa.
In our town, wood can ___________ a fire.
In the past five years China ________ great _________.
They talked for about an hour of things and persons _____ they remembered in the school.
Don’t be in a hurry. We are supposed ____________ this problem step by step.