—How do you think he managed to improve his English in such a short time?
— four hours on it every day．
A. Because of spending
B. To spend
C. By spending
D. Spending
网友回答
A. Because of spending
B. To spend
(答案→)C. By spending
D. Spending
解析：问句用到的疑问词是how表方式所以答语要用介词短语By spending作方式状语。句意：你认为他是怎样在短时间内提高英语的？通过每天花费四小时（练习做到的）。