When Mary stood up to answer the question , she was _____at first but soon relaxed.

A．nervous

B．happy

C．mad

D．athletic

属于龋病三级预防的内容是（）

A.六龄齿的窝沟封闭

B.龈下洁治术与根面平整

C.对根尖炎的牙齿进行根管治疗

D.戒烟、控酒

E.可疑龋的预防性充填