单项选择题
A.Δf/f≤10% B.Δf/f≤15% C.Δf/f≤20% D.Δf/f≤25%
A.K1.0 B.K1.2 C.K1.7 D.K1.5
A.K1.0 B.K1.2 C.K1.3 D.K1.4