单项选择题
A.R ＝2.00008Ω，U rel ＝9×10-5Ω，k =2B.R ＝2.000075（45）Ω，k =2C.R ＝2.000075Ω，U rel ＝4.5×10-5Ω，k =2D.R ＝（2.000075±4.5×10-5Ω），k =2
A.ms=100.0101025gB.ms=（100.01025±0.0035）gC.ms=100.01g±0.70mg，k =2D.ms=100.01025g，U =0.70mg，k =2
A.y =0.14B.y =0.15C.y =0.1D.y =0.2