55.Was it----the professor regarded as the brightest ones?

55.Was it____the professor regarded as the brightest ones?
A.them which B.them who C.he who D.that that

选B.them who
【解析】强调句结构是it 引导的句子.
It is (was) 被强调部分+ that (who) + 句子其他部分.
以上此句是强调句型的疑问句结构
Is(Was) it 被强调部分+who( that)+ 句子其他部分?
由此可排除A,因为A项不含有who或that,不能构成此结构.句子后面the brightest ones”说明是复数,故可排除C,因为里面的he是单数.
事实上D中that也是单数,也可排除.
对于B和D,可进一步可以这样分析,由于强调句结构里,当省略It is (was)和that (who) 后句子还是一个完整句子,都含有各成分.所以,省略了它们后的陈述句句子变成：
the professor regarded _them__as the brightest ones.从而可看出原句是强调宾语成分的强调句型疑问句结构.
“___”里如果是that将说不通,只能是them“.
即原句为：The professor regarded them as the brightest ones.教授把他们看成是最聪明的人.故答案为B.them who