单项选择题
A.1m2=25.4in2 B.1in2=25.4m2 C.1in2=645.6m2 D.1in2=6.4516×10-4m2
A.dm2 B.cm2 C.km2 D.mm2
A.kN,N B.kN,n C.Kn,n D.kgf,kn