起动次数（），要求起动时间（）和起动转矩较大的生产机械，常采用绕线型异步电动机。
参考答案：频繁；很短
朝核问题中当事国朝鲜与我国接壤于
A．东部
B．西部
C．南部
D．北部
Though difficult, I _____ him find a job, which made him very pleased. [ ]
A. tried to help
B. managed to help
C. tried helping
D. succeeded to help
