We should prevent pollution ________ happily.
We believe scientists will ________a way to solve the problem of air pollution.
His wife ______ his children was invited to the party.
—What’s the matter _______Mike? He is wet through.—His car ran _______the river.
Please ask ________ not to skate on the thin ice. It’s very dangerous.
Wouldn’t it be ______ wonderful world if we could live in ______ peace?