The voyages of travellers before the 17^th century show that they were not ________ the sea even though they didn’t have modern navigational aids
A.at the expense ofB.at the risk ofC.in the way ofD.at the mercy of在线课程D
短语辨析. A.以……为代价； B.冒着……的危险 C. 妨碍；关于……方面 D. 受……支配。句意：十七世纪前的旅行者的航行告诉我们尽管他们没有现代助航设备，他们也不受大海支配。故选D。