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

游客2023-11-13 25

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引导的时间状语从句是一般过去时，所以主句应该采用过去完成时。

转载请注明原文地址:https://tihaiku.com/zcyy/3184678.html

相关试题推荐

随机试题

最新回复(0)

______theheavyfoghasdelayedtheflight,sotheywouldn’tarriveontime.A、Im