The riseof oil prices made scientists search for new energy resources ______ oil

The mother often tells her son to be a good boy, warning him to _____ trouble.

How long have you ______ ?

to __ to the south, so now, I amused to __ in a hot climate.

You didn’t come to the meetingyesterday afternoon, did you —No, I ________ at thestation for my uncle from Beijing.