以下关于牙体预备中牙髓保护的说法正确的是（）

A.牙体预备分次完成

B.轻压磨切

C.尽量少磨牙

D.预备时间歇、短时磨切

E.水雾冷却

The old man was telling a funny story, surrounded by many kids, _________ with fascination.

A．all of whom listened

B．all of whom listening

C．all of them listened

D．all of them were listening