you may have you should gather your courage to face the challenge .A. However serious a

问题补充：

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

A. However serious a problem

B. Whatever serious a problem

C. However a serious problem

D. No matter how a serious

答案：

(答案→)A. However serious a problem

B. Whatever serious a problem

C. However a serious problem

D. No matter how a serious

解析：考查让步状语从句。因为后面直接接了形容词serious，说明前面使用how；因为what后面接名词或者名词短语。句意：无论你遇见如何严重的问题，你都应该鼓起勇气面对挑战。故A正确。