_____ cleans the blackboard should be praised.

1:___C__ cleans the blackboard should be praised.
A:anyone B:who C:the one who D:Those who
解析:先行词the one,引导词who,定语从句：who cleans the blackboard ,引导词在定语从句中做主语.
2：This is ___C__I wanted.
A:which B:the one what C:the one D;the which
解析：先行词the one,引导词that(省略),定语从句：(that)i wanted,引导词在定语从句中做宾语,可以省略.
3：The magazine _C__Betty paid one dollars was very good.
A:that B:which C:for which D:to that
解析：先行词：magazine,引导词which,定语从句 for which Betty paid one dollars ,which在定语从句中做宾语.Pay for是固定词组,介词for提前,放在引导词which之前
4.The two things __B___they felt very proud were Jim,s gold watch and Della,s hair.
A:about which B:of which C:in which D:for which
解析：先行词：two things ,引导词which,定语从句 of which they felt very proud ,which在定语从句中做宾语.proud of是固定词组,介词of提前,放在引导词which之前
5.She had two daughters,_D___became doctors.
A:all of themB:all of whom C:both of them D:both of whom
解析：先行词two daughters,引导词whom,定语从句 both of whom became doctors.此为非限制性定语从句
额自己的意见,仅供参考,嘿嘿,有问题可以加额QQ呦：1341542208,身份验证：英语交流

C。 cleans 所以主语是单数。
C. 没有the which的用法，也没有the one what的用法，所以排除。
不选which，因为它前面没有需要指定的
C。 因为 paid for the magazine，所以for这个介词不能省。
B。 feel proud of sth. 所以of不能去掉。
C。 如果有both of who...

C(因为cleans带着s，所以主语单数形式，选C)