单项选择题直流输出母线的正极对地、负极对地的绝缘电阻应大于( ) A. 1MΩ B. 2MΩ C. 3MΩ D. 5MΩ
单项选择题Which one is not a franchise movie? A、Jurassic Park B、X Man C、The Avengers D、Dead Poets Society