问题
选择题
I’m afraid he is more of a talker than a doer, which is _________ he never finishes anything.
A．that
B．when
C．where
D．why
答案
答案：D
题目分析：句意：恐怕他是一个说大话的人，这正是为什么他从未做成事情的原因。Which引导的是非限制性定语从句，从句中is后面是表语从句，根据句意可知D正确。