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Before the first non-stop flight made in 1949, it______necessary for all planes
Before the first non-stop flight made in 1949, it______necessary for all planes
游客
2024-09-07
20
管理
问题
Before the first non-stop flight made in 1949, it______necessary for all planes to land for refueling.
选项
A、would be
B、has been
C、had been
D、would have been
答案
C
解析
由before引导的时间状语表示过去,所以主句应该采用过去完成时,表示“过去的过去”。
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