The question that puzzled them is ____ they can get rid of the air pollution in the area.

The doctor was _____immediately the little boy fell off a ladder and hurt himself.

How do you find the health club — I ______. Everyone is saying itsmanagement is going from bad to worse.

_______, I lost heart in English learning, but my teacher said to me, “Keep on working hard, and you’ll succeed ________.”

下列各句中，加点词语使用恰当的一项是（ ）