My uncle is quite worn out from years of hard work. He is no longer the man ___ he was fifteen years ago. (2011英语专四51题)
A. Which B. whom C. who D. that
答案：D
解析：关系代词在定语从句中做表语时，无论指人还是指物，通常用that，不用which或who，且that也可以省略。
再如：
1、China is not the country (that) it was. 中国不是从前的那个国家。
2、Mary is no longer the girl (that) she used to be. 玛丽不是过去的那个女孩了。