_______ was known to them that the boss had broken his promise______ he would give them a rise.

A．What; what

B．It; which

C．It; that

D．As; that

青少年牙周炎的好发牙位为(　　)。

A．尖牙

B．第二磨牙

C．前磨牙

D．第一磨牙和切牙

E．所有后牙