答案　A

解析　句意：你认为野营和爬山对我们的身体健康很有好处吗？be of benefit to...对......有益处。

18.Your mother________，however，say that to us that day.

A.does B.did C.is doing D.was doing

答案　B

解析　句意：然而，你母亲那天的确对我们说了那件事。强调谓语动词，用助动词，结合时态为过去时，故用did。

19.In front of our school ________，where a lot of people play or take exercise at any time.

A.does a park lie B.is a park lie C.a park lies D.lies a park

答案　D

解析　当表示方位的介词短语位于句首时，句子要用完全倒装形式，即全部的谓语放在主语之前，in front of 是介词短语，该句要完全倒装，故选D。

20.We________him to stop surfing the Internet，but he wouldn't listen.

A.persuaded B.tried to persuade C.suggested D.demanded

答案　B

解析　句意：我们努力说服他停止上网，但是他不听。try to persuade努力说服，不一定听从；persuade说服；suggest建议，后常接动名词；demand要求。

21.I bought a dress for only 10 dollars in a sale; it was a real ________.