单项选择题
A.电压 B.电流 C.电功率 D.电阻
A.0.001/℃ B.0.002/℃ C.0.005/℃ D.0.008/℃
A.R=r1+r2+…+rn B.R=r1r2/(r1+r2) C.R=1/r1+1/r2+…+1/rn D.R=r2/r1+r3/r2+…+rn/rn-1