问题补充：
He spent thirty minutes in finishing his homework.
A. It took him half an hour to finish his homework.
B. It takes him half an hour to finish his homework.
C. It cost him half an hour to finish his homework.
D. He spend half an hour to on finishing his homework.
答案：
(答案→)A. It took him half an hour to finish his homework.
B. It takes him half an hour to finish his homework.
C. It cost him half an hour to finish his homework.
D. He spend half an hour to on finishing his homework.
解析：句意：他花了30分钟完成作业。句式It takes sb. sometime to do sth.做某事花费某人多少时间。从原句spent用的过去式，所以take用过去式took，故选A.
