Walking alone in the dark the boy whistled to his courage.A. hold upB. keep upC. set upD.

问题补充：

Walking alone in the dark, the boy whistled to his courage.

A. hold up

B. keep up

C. set up

D. take up

答案：

A. hold up

(答案→)B. keep up

C. set up

D. take up

解析：动词短语辨析。A举起，支持；B保持；维持；激发；C建立，成立；D占据，从事于；开始做；句意：独自一人走在黑暗的街上，那个男孩吹起口哨来鼓起自己的勇气。故B正确。