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
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The fleet made several expeditions _____ the exploration was stopped. [ ]
A. when
B. before
C. while
D. since
答案：B
sinl00πt（V），则下列说法中正确的是（ ）
V