问题
选择题
The fleet made several expeditions _______ the exploration was stopped.
A．when
B．before
C．while
D．since
答案
答案：B
考查连词，A. when当…时候，B. before在…之前，翻译时可以做为：…才， C. while当…时候，然而D. since自从，句意是：船队进行了几次短途旅行之后，探险才结束。选B。