| Electric Backpack Backpacks are convenient. They can hold your books, your lunch, and a charge of clothes, leaving your hands free to do other things. Someday, if you don’t mind carrying a heavy load, your backpacks might also power your MP3 player, keep your cell phone running, and maybe even light your way home. Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole, Mass. , have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions, search and-rescue operations, and scientific field studies, people rely increasingly on cell phones, global positioning system (GPS) receivers, night-vision goggles, and other battery-powered devices to get around and do their work. The A. they can be very large. B. they can hold as many things as you want to carry. C. your hands are freed to do other things. D. you do not have to carry things with you. [判断题]在特殊情况下, 主提升机操作工可以离开工作岗位,调整制动器。( )
A.正确 B.错误 [单选题]下列哪种情况下不属于奎宁丁的禁忌症
A.完全性房室传导阻滞 B.充血性心力衰竭 C.新发病的心房纤颤 D.严重低血压 E.地高辛中毒 [单项选择]“壮水之主，以制阳光”体现的治则是（）。
A. 阴病治阳 B. 阳病治阴 C. 热者寒之 D. 寒者热之 E. 阳中求阴 [单选题]光伏组件安装作业开始时，应由（）将组件板抬于支架上，禁止单人挪用组件板，并按照图纸规划安放牢固。
A.专人 B.两人 C.工作人员 D.施工人员 [单项选择]胶片特性曲线上的斜率可以判别什么参数？（）
A. 感光度 B. 衬度 C. 温度性能 D. 密度 我来回答: 提交
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