我把我的答案以及思考放在后面，方便大家对症下药，请指出我哪里错误，谢谢
1.Is your mother_______?She looks really young?D 我认为指她妈妈40岁，而且变成复数
A.in her fifty B.in the fifty C.in her fifties D.in the fifties
2.Mary's never been abroad,_______?A前否后肯，而且有's代表了is 。
A.is she B.isn't she C.has she D.hasn't she
3.----How long has his daughter _______ her school?我选B，how long后面用延续性动词
----since last week.
A.been away from B.be away from C.left D.be off
4.----The river has been so seriously polluted.C 我估计是乱选，而且这句有两个单词不会
----Yes.Something_____to stop people from pouring dirty water into it.
A.should be done B.can do C.may be done D.must do
5.Simon is as_______as Tony,but he runs much________.C 我知道错哪了...as 原形as
much+比较级 所以选D..
A.fatter;faster B.fat;fast C.fatter;fast D.fat;faster