Some people are bad at recalling names and faces, so it's possible that they have a condition called face blindness, ______ people suddenly have trouble recognizing family members, friends or even themselves．

A．for which

B．which

C．where

D．of which

表面活性剂在药剂中常作

A．增溶剂

B．乳化剂

C．润湿剂

D．润滑剂

E．去污剂