【题目】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】B
【解析】句意：独自在黑暗中行走，男孩吹口哨保持勇气。A.hold up“举起”；B.keep up“维持，使不低落”；C.set up“建立”；D.take up“拿起”。根据句意，选B。