【题目】They were lost at sea, ____ wind and weather.
A.at the cost of
B.at the risk of
C.at the sight of
D.at the mercy of

【答案】D
【解析】句意：由于受到风和天气的影响，他们在海上迷路了。at the cost of “以……为代价”；at the risk of“冒着……的危险”；at the sight of “一看见……就”；at the mercy of“受……支配”。迷路的原因是由于风和天气。故选D。