问题补充：
Willpower is a kind of quality, is it takes to do anything well.
A. what; which
B. what; what
C. which; which
D. which; what
答案：
A. what; which
B. what; what
C. which; which
(答案→)D. which; what
解析：D句意：意志力是一种品质，是做好任何事情所需要的。“isit takes to do anything well”为非限制性定语从句，先行词为willpower，先行词在定语从句中作主语，故用which引导；“isit takes to do anything well”这一定语从句中又含一表语从句，即“it takes to do anything well”，该表语从句缺少宾语(作takes的宾语)，表示“事物”且语境中并无选择含义，故用what引导。
