题目

______ they are brothers, they don't look like each other at all.    A. Because    B.  Though       C. When         D.   As 答案：B4．某电动机的工作效率是83%，从能量转化看，它表示电动机工作时（　　）A．总共消耗了83%的电能B．将83%的电能转化成机械能C．将83%的电能转化成内能D．将83%的机械能转化成电能