定语从句练习题(帮我解释一下理由）

定语从句练习题(帮我解释一下理由）
1)It may pollute the grass that ________________
A.animals are fed on B.feeds animals
C.animals are fed D.feed on animals
2)She had two daughters ,________ became doctors
A.all of them B.all of whom
C.both of them D.both of whom (w为什么这边要用whom_)
1.A 2.D