CH50试验中，加入少量的钙、镁离子的目的是（）

A.保持溶液的等渗压

B.维持合适的pH

C.抑制细菌的生长

D.抑制溶血反应

E.有助于补体的激活

--Do you think that we should prepare for our exam in advance?

-- Of course. _________.

A．Actions speak louder than words

B．Better late than never

C．A good beginning is half done

D．The early bird catches the worm(虫)