下列参量中不属于电力系统电磁参量的是（）。 ["功率","电流","频率","电压"]
An obstruction on a helideck is any object that might present a hazard to the（）. ["rotor blades and landing gear","unloading of passengers","loading of cargo","pilot's visibility"]
导游小李接待了一个老人团，在行程即将结束时，老人们提出品尝当地的正宗小吃。小李便带老人们到一个水上餐厅吃海鲜餐，老人们也一致赞同。可在当天返回酒店途中，有的老人就出现了头晕、恶心、浑身乏力的症状，有的老人还出现了呕吐和腹泻的情况。请问小李此举有哪些不妥之处，应该注意些什么？
以下哪项不能以人寿保险单做质押（） ["投保人选择保险单中的保险费自动垫缴条款","保险单的第一顺序受益人已变更为华夏银行","父母为其成年子女投保的人身保险","保险费分期缴付的，保费至少缴足两年"]
AN ILLNESS PREFERABLY OF AN INFECTIOUS NATURE SEIZING MORE THAN TWO PERSONS ON BOARD AT THE SAME TIME defines（）. ["Disease of Crew","Crew illness","Group illness","Mass disease"]
员工福利的特点是什么？
