服用铋剂时的粪便颜色为（）

A.鲜红色

B.暗红色

C.白色或灰白色

D.绿色

E.黑色或柏油色

____ you ask many different questions will you acquire all the information you need to know．

A．If only

B．As far as

C．So long as

D．Only if