问题补充：
The school board is made up of parents who to make decisions about school affairs.
A. had been elected
B. had elected
C. have been elected
D. have elected
答案：
A. had been elected
B. had elected
(答案→)C. have been elected
D. have elected
解析：elect意为选举，推选，它的主语是关系词who所代指的parents，该句句意为，学校的董事会由那些被推选来就学校事务做决定的父母组成的。根据句意可知，父母和elect之间是被动关系，因此排除BD选项。因为主句is made up of是一般现在时，故排除A项，选择C项，表示已经被推选出来。
【考点定位】考察时态语态。
