单项选择题
A.70% B.75% C.80% D.85%
A.3,3,0.3,2B.2,2,0.3,2C.3,2,0.3,2D.3,2,0.3,3
A.1/2~1/3B.1/3~1/4C.1/4~1/5D.1/5~1/6