黏固烤瓷冠修复体前．修复体组织面需做的处理是（）

A.清洁

B.干燥

C.酸蚀

D.消毒

E.涂分离剂

Besides the electrons, an atom also contains positive electrical particles______total charge must be equal to that of the electrons.

A．which

B．that

C．whose

D．of which