________you may have，you should gather your courage to face the challenge.

________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

答案及解析： C

解析：

考查状语从句。分析题干可知逗号前是让步状语从句，what不能用来引导状语从句，所以排除B、D两项；

however+adj.+a/an+单数名词＝whatever+a/an+adj.+单数名词，句意：不论你的问题有多严重，你都应该鼓起勇气，接受挑战。故C项正确。