The children, had played the whole day long, were worn out.
A. all of what
B. all of them
C. all of whom
D. all of which
网友回答
A. all of what
B. all of them
(答案→)C. all of whom
D. all of which
解析：考查非限制性定语从句，句意：那些玩了一整天的孩子们，都已经累坏了。首先先行词是the children是指人的，排除AB，them不能引导从句，这里是不定代词all+介词+whom引导定语从句，选C。