A.2:1 B.1:1 C.1:2 D.1:3
A.(L初讀數(shù)-L終度數(shù))×1.5 B.L初讀數(shù)-L終度數(shù) C.(L初讀數(shù)-L終度數(shù))×2 D.L終讀數(shù)-L初度數(shù)