单项选择题
A.e1c1F1=e2c2F2 B.c1F1=c2F2 C.c1/c2=F2/F1 D.c1/c2=F1/F2
A.10CrMo910 B.13CrMo44 C.χ19CrMOVNbN11 D.15Mo3