单项选择题
A.1.5~2.5 B.2.5~4.2 C.3.5~4.2 D.3.5~7
A.1/4~1/2 B.1/4~1/3 C.1/3~1/2 D.1/3~2/3
A.15% B.30% C.45% D.55%