水的硬度用下列哪项(mg/L)表示

A、CaO
B、MgCO[img=~/QImg/2013-10-14-11-46-19/image003.jpg]
C、CaCO[img=~/QImg/2013-10-14-11-46-19/image003.jpg]
D、CaCl[img=~/QImg/2013-10-14-11-46-19/image002.jpg]
E、Ca(HCO[img=~/QImg/2013-10-14-11-46-19/image003.jpg])[img=~/QImg/2013-10-14-11-46-19/image002.jpg]