—Excuse me, could you tell me where the post office is?

—__________, but I’m a stranger here．

A．I’m not sure

B．I’m sorry

C．That’s righ

D．I’m afraid not

下列哪种材料可单独用作软膏基质

A．植物油

B．液状石蜡

C．固体石蜡

D．蜂蜡

E．凡士林