[单选题]

某老年人牙龈退缩的牙面中未患龋牙面有40个,患根面龋的牙面10个,因根龋充填的牙面10个,该老年人根龋指数为()

A.20%

B.25%

C.33%

D.37%

E.40%

参考答案与解析: