【2008.10】When the engine broke down，the boat’s crew found themselves ______ of the wind．
A、at the cost
B、at the mercy
C、at the rate
D、at the moment
【正确答案】：B
【题目解析】：本题考查词组的固定搭配。at the cost of：以…为代价；at the mercy of：任凭…的摆布；at the rate：以…的比率；at the moment：此刻，…的时刻。
