Before the first non-stop flight made in 1949, it______necessary for all planes

游客2024-09-07 24

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”。

转载请注明原文地址:https://www.tihaiku.com/zcyy/3747336.html

相关试题推荐

随机试题

最新回复(0)

Itwasreportedthata73-year-oldmandiedonanEtihadflight_____toGermanyf