DNS服务器为什么会向其它DNS服务器求助？求助的方法有哪些？
A venetian vent or rice ventilator is used in stowage of which cargo?（）. ["Bagged cargo","Bulk grain","Bulk rice","Refrigerated good"]
如何保证电能质量的频率指标？
品牌客户跨分行关系调整，调整的是客户的（） ["人工助理关系","远程助理关系","地区主管关系","全国主管关系"]
A drop in compression pressure in one cylinder of a diesel engine can be caused by（） ["a leaking fuel injection nozzle","a clogged air filter","early fuel injection","burned valve"]
在多个网络中实现DHCP服务的方法主要有几种？各有什么特点？
