There is a peaceful and calm _____________ in the hall, and everyone seems to be in high spirits.

A．atmosphere

B．air

C．stage

D．performance

牙周炎时牙槽骨破坏的形式有（）。

A.水平型吸收

B.垂直型吸收

C.凹坑状骨吸收

D.反波浪形骨缺损

E.以上都不对