解析:at the mercy of:在……支配下。例句,The ship was at the mercy of the waves.(这艘船任凭风浪摆布。)at the expense of:以……为代价,靠牺牲……;at the risk of:冒……的危险;in the way of:碍……事,挡道。
例句:
1.He devoted his time to football at the expense of his study.
(他牺牲学习把时间都花在足球上。)
2.Her social life got in the way of her study.
(她的社交生活妨碍了她的学习。)
3.We did this at the risk of our lives and liberties.