To test eggs, _____ them in a bowl of water: if they float they’re bad, if they sink they’re good.

A．put

B．putting

C．to put

D．to be putting

牙周病预防重点在

A．控制致病菌

B．消除菌斑

C．牙石的控制

D．控制唾液菌量

E．控制菌斑