机车用直流电机定额，分为连续定额、（）定额、断续定额及等效定额4类。
参考答案：小时
袋子里有6张纸条，每张纸条上分别写着“学习”“劳动”“工作”“生活”“唱歌”“喝水”。任意摸出1张纸条，有几种可能的结果？
—There are many old houses in Beijing, aren’t there?
—______ . It’s a city with long history.[ ]
A. Yes, they are.
B. Yes, there are.
C. No, there aren’t.
