单项选择题

Before the first non-stop flight made in 1949, it （） necessary for all planes to land for refueling.

A．would be
B．has been
C．had been
D．would have been

<上一题 目录 下一题>
热门 试题

单项选择题
There was （） to prevent the accident.

A．something could do
B．nothing we couldn't do
C．anything we could do
D．nothing we could do
相关试题