In the face of failure it is vital that we should keep up good state of mindA. a; /B.

问题补充：

In the face of failure, it is vital that we should keep up good state of mind．

A. a; /

B. /; a

C. the; /

D. /; the

答案：

A. a; /

(答案→)B. /; a

C. the; /

D. /; the

解析：考查冠词。Failure当失败讲，是不可数名词，不加冠词；state当状态讲，是单数可数名词，要用不定冠词a 修饰。所以选B。