问题补充：
you may have, you should gather your courage to face the challenge.
A. However a serious problem
B. What a serious problem
C. However serious a problem
D. What serious a problem
答案：
A. However a serious problem
B. What a serious problem
(答案→)C. However serious a problem
D. What serious a problem
解析：句意：无论你有多么严重的问题，你都应该鼓起勇气勇敢面对。What 引起的感叹句是What +冠词+形容词+名词+主语+谓语+……；However+形容词+冠词+名词+主语+谓语……；这里是However引起的让步状语从句，故选C。
