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
C. However serious a problem
D. What serious a problem
解析：C
解析根据句意“无论你有多么严重的问题，你都应该鼓起勇气面对挑战。”，而however表让步时其顺序应是：however＋形容词＋主语＋谓语。however作连接副词，相当于no matter how，后接形容词或副词，意为“无论，不管”，引导让步状语从句，其顺序为“however＋形容词、副词＋主语＋谓语”。
