呼吸衰竭的患者临床上出现最早的症状是（）。

A.胸部疼痛

B.呼吸困难

C.咯血

D.发绀

E.精神错乱

——Did you stay up very late last night?

——No，It was not 10 o’clock yet ____I went to bed.

A．when

B．until

C．that

D．while