He was hiding behind the door _________ he could see what was happening.

A. which               B. from where        C from which       D. where

关于补钾原则，下列哪种说法正确（）.

A.补钾的浓度宜低于0.3％

B.补钾的速度一般不宜超过20mmol/h

C.每日补钾量不宜超过100～200mmol

D.每小时尿量超过40ml后，再从静脉输给氯化钾溶液

E.以上各项均对