全电路欧姆定律的表达式是（） A: U=IRO B: I=E/（R+RO） C: U=E+IRO D: I=（U-E）/RO

全电路欧姆定律的表达式是（） A: AU=IRO B: BI=E/（R+RO） C: CU=E+IRO D: DI=（U-E）/RO

Permanent magnetism is caused by（）. A: operation of electrical equipment and generators on board ship B: the earth's magnetic field affecting the ship's hard iron during construction C: the horizontal component of the earth's magnetic field acting on the horizontal soft iron D: the vertical component of the earth's magnetic field acting on the vertical soft iro