—I have to be at the office by noon tomorrow. My co-workers are taking me out for a final good-bye lunch.

— ________ Where are you going to eat?

—I don’t know. They want to treat me.

A．I don’t know.

B．How nice!

C．It’s my pleasure.

D．It’s none of my business.

影响腰麻麻醉平面相对最小的因素是（）。

A.药物比重

B.患者体位

C.注药速度

D.药物剂量

E.药物浓度