问题

the first nonstop flight made in 1949, it_____necessary for all planes to land for refueling.
A:would be
B:has been
C:had been
D:would havebeen
B:has been
C:had been
D:would havebeen
正确答案是:
同类题型
I enjoy reading the novel that was written by Zhang Ailing.
Mr. Li often us to do more exercise. It’s good for health.
erribly sorry, Lucy.I’ve left your notebook at home.—_____ I reminded you last night.
Li Hua is a ______player. He can playfootball________.
Eating too much fat and sugar can heart disease and high blood pressure.