单项选择题
A.>95% B.>96% C.>97% D.>98%
A.≦3vs/cm2 B.≦4vs/cm2 C.≦5vs/cm2 D.≦6vs/cm2
A.6-8mg/L B.9-10mg/L C.10-11mg/L D.7-12mg/L