The only candidate______can hope to defeat him finally quits.
A. who
B. which
C. that
D. when
这是这道题给出的解析
The only candidate that can hope to defeat him finally quits.
(唯一能指望打败他的候选人最终退出了。)
解析✨
定语从句中，当先行词由形容词的最高级或序数词last, next,only等限定词修饰时，关系代词只能用that。
eg:This is the only problem that remains to be settled.
（这是唯一有待解决的问题。）
当先行词是all, everything.anything,nothing, little,much等时，也只能用that.
eg:The thief handed everything that he had stolen to the police.
(小偷把他偷来的所有东西都交给了警察。)
综上所述：本题选C. that.
我想问，这里指的是that和which的用法。当先行词被the only修饰时，其关系词只能用that，指的是先行词是物非人时，只能用that不能用which，不包括先行词是人的情况，先行词是人时本来就不能用which故不在讨论之列，所以可以用that也可以用who，是这样吗