A.磨損 B.疲勞損壞 C.腐蝕損壞 D.偶然損傷
A.(一級車數(shù)+二級車數(shù)+三機車數(shù))÷各級車數(shù)總和 B.2(一級車數(shù)+二級車數(shù)+三機車數(shù))÷各級車數(shù)總和 C.(3×一級車數(shù)+2×二級車數(shù)+1×三機車數(shù))÷各級車數(shù)總和 D.(1×一級車數(shù)+2×二級車數(shù)+3×三機車數(shù))÷各級車數(shù)總和
A.四分之三 B.五分之三 C.三分之二 D.二分之一