The fact showed thatthevoyagesof travelersbeforethe17th...

问题详情：

The fact showed  that the voyages of  travelers before the 17th century were not ______the sea even though they didn't have modern navigational aids.

A. at the expense of                    B. at the risk of     

 C. in the way of                        D. at the mercy of 

【回答】

D

知识点：介词

题型：选择题