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阅读下面的短文。每篇短文的后面有五个问题，每个问题有四个备选答案。请根据短文的内容选择最佳答案。每个试题计3分,共计15分。 Windows not only let light in to cut down an electricity use for lighting，but the light coming through the window also provides heat.However，windows are not something people typically associate with being a cutting edge1 technology.Researchers are now working on new technologies that enable a window to quickly change from clear to dark and anywhere in between with a flip of a switch2. Yet，windows are the weak link in a building when it comes to energy and temperature control.In the winter，cold air leaks in.When its hot and sunny，sunlight streams in.All of this sunlight carries lots of heat and energy.And all of this extra heat forces people to turn on Windows have been a major focus of energy research for a long time. Over the years，scientists have come up with a variety of strategies for coating，glazing，and layering windows to make them more energy efficient.Smart windows go a step further.They use chromogenic technologies which involve changes of color. One important feature that makes a smart window so smart is that it has a sort of memory. All it takes is a small jolt of voltage to turn the window from one state to the other.Then，it stays that way.Transitions take anywhere from 10 seconds to a few minutes，depending on the size of the window.The development of smart windows could mean that massive air conditioning systems may no longer need.In the future, Granqvist says,our buildings may look different. | 
