—Why does Mary look so worried today?

—I’m not sure, but she _____ a small accident driving here.

A．must have

B．might have

C．must have had

D．might have had

具有公共卫生特征的防龋措施是（）

A.氟化饮水

B.氟化牛奶

C.氟化泡沫

D.氟片

E.窝钩封闭