—Could you tell me               ?

—Sure. Just go straight and turn right. You'll find it on your left.

A．why I have to go there

B．when can I get there

C．where I can find the nearest restaurant

D．what I can do

滴眼剂中加入下列物质其作用是

氯化钠（）

A．调节渗透压

B．调节pH值

C．调节粘度

D．抑菌防腐

E．稳定