Question

The children,____ had played the whole day long, were worn out. A．all of what B．all of whic.

Answer 1

D
句意：孩子们都累坏了，他们都玩了一整天。非限定定语从句，关系代词指人且在介词之后故用whom。
【考点定位】定语从句关系词的选用。注意C项，原句主干
children
were
worn
out，即为完整的句子，那么空白处需要填连词用以构成从句，故C项的代词不能选择。