Ten minutes later，a bus ______ and everybody got on it.

Must I finish the exercise at school? — No, you don’t have to. You do it at home.

A new factory will be set up ___ a year. [ ]

What would you do if _________ eighty-year-old man fell down in front of you? —-I don’t know. Maybe I will help him.

He lost a set _____ keys.[ ]