I heard his voice trembling did I realize what trouble he was in.
A. Only when
B. Until when
C. No sooner had
D. Hardly had
网友回答
(答案→)A. Only when
B. Until when
C. No sooner had
D. Hardly had
解析：考查倒装句的用法：only +状语在句首时，主句要部分倒装，句意是：只有我听到他颤抖的声音我才知道他有什么样的麻烦。选A。