Before charging a refrigeration unit, the refrigerant charging lines should be（） ["flushed with clean refrigerant oil","purged with the refrigerant","washed with an ammonia and alcohol solution","grounded to compressor"]
什么是摩擦传动？
提高植物根冠比的水肥措施是什么？（） ["多施氮肥，少浇水","多施磷肥，多浇水","多施氮肥，多浇水","多施磷肥，少浇水"]
对署名举报人实行“三到位”原则是指（）。 ["承办单位领导到位","承办人到位","与被举报人接触到位","与举报人接触到位"]
以下哪些外部因素会影响现代运动训练目标（） ["竞赛对手的情况","竞赛规则的变化","竞赛场地、器材的特点","竞赛分组情况等"]
当配电网线路继电保护和安全自动装置出现异常时应如何处理？
