建立平面控制网的方法有哪几种？各有何优缺点？
Internet Protocol videoconferencing (IP/VC) provides which two business benefits? （） [" Reduced travel time for instructors responsible for different geographic sites"," Real-time discussions of patient information among remote medical teams"," Improved morale and reduced turnover among employees who receive timely business Updates"," Increased sales and customer satisfaction due to current product information disseminated simultaneously to a global sales force by headquarter"]
电焊机一次侧电源线长度一般不超过（）m。 ["15","10","5","3"]
GPS地面监控跟踪站又被分为主控站、监控站和注入站，其中主控站有（）个。 ["1","2","3","4"]
长期大量应用呋喃妥因的不良反应是（） ["泌尿系统损害","周围神经炎","再生障碍性贫血","过敏反应","二重感染"]
季相
