17. 有一部三相、60Hz、10HP之感應電動機,當滿載的轉速為1140rpm時,請問該感應電動機之極數與轉差率應為下列何者? (A) 6極,0.05 (B) 4極,0.44 (C) 6極,0.66 (D) 4極,0.03