单项选择题
A.0.25-0.35kgf/cm2 B.0.40-0.50kgf/cm2 C.0.60-0.70kgf/cm2 D.1.5/kgf/cm2
A.0.5 B.1 C.1.5 D.2
A.50% B.60% C.70% D.80%