—Your spoken English is so good. Have you been abroad?

—Yes. I     in London for two years.

A．have stayed

B．stayed

C．had stayed

D．have been staying

下列不是颌骨缺损修复原则的是（）。

A.早期、系列修复

B.尽可能恢复生理功能

C.尽量保护预留组织

D.修复体有足够固位和轻巧

E.最好术后即刻修复