题目

（·温州市八校高三月联考）    10. Mr. Smith would have come to see you if it had been possible, but he __________ so busy.  A. was          B. had been             C. has been             D. were 答案：A有一台电动机额定电压为380V，正常工作时通过的电流是5A，输出的功率是1.5kW，问：（1）该电动机的效率是多少？（2）试分析该电动机能量的转化．