Is this man______ the policemen have been looking for?

Is this man______ the policemen have been looking for?
A.that B.whom C.the one D.which
不能选B.
因为this man 是主语,is 是系动词,后面跟表语.该表语由句子充当,所以该句叫表语从句.
而表语从句是名词性从句（名词性从句有主、宾、表、同位语从句四种）.
在名词性从句中whom的词义是"谁".
例如：Did you ask me whom the man is?你是在问我那个人是谁吗?
在定语从句中whom代替表示人的先行词
（即定语从句修饰限定的词）,译成先行词的意思,whom在定语从句中做宾语.
例如：I know the man whom you mean.我认识你所的那个人.
Is this man *the man=the one* whom the policemen have been looking for?
如果还不懂的话,我肯定能讲懂.加油!