---- Flight 551 for Dallas ________. I must be off now.

------Have a pleasant trip then.

A．is being announced

B．has announced

C．was announcing

D．had been announced

有关前臂的解剖错误的是（）。

A.尺桡骨均有一定弧度

B.桡骨沿尺骨旋转

C.前臂旋转幅度可达180°

D.两骨间有骨间膜

E.骨间膜对尺桡骨起稳定作用