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  3. Li-Fi, an alternative to Wi-Fi that transmits data using the spectrum of visible light, has achieved a new breakthrough, with UK

Li-Fi, an alternative to Wi-Fi that transmits data using the spectrum of visible light, has achieved a new breakthrough, with UK

admin2017-08-11  7
问题     Li-Fi, an alternative to Wi-Fi that transmits data using the spectrum of visible light, has achieved a new breakthrough, with UK scientists reporting transmission speeds of 10Gbit/s—more than 250 times faster than ’superfast’ broadband. The fastest speed【C1】______reported was 3Gbit/s, achieved earlier this year in Germany. Chinese researchers also claimed this month to have【C2】______a 150Mbp/s connection, but some experts were doubtful without seeing further【C3】______
    The term Li-Fi was【C4】______by Edinburgh University’s Prof Harald Haas【C5】______the technology is also known as visible light communications (VLC). Many experts claim that Li-Fi represents the future of mobile internet【C6】______its reduced costs and greater efficiency compared to traditional Wi-Fi. Both Wi-Fi and Li-Fi transmit data【C7】______the electromagnetic spectrum, but【C8】______Wi-Fi utilizes radio waves, Li-Fi uses visible light. This is a【C9】______advantage in that the visible light is far more plentiful than the radio spectrum (10,000 times more in fact) and can achieve far greater data【C10】______Li-Fi signals work by【C11】______bulbs on and off【C12】______quickly—too quickly to be noticed by the human eye. This most recent breakthrough builds upon this by using tiny micro-LED bulbs to【C13】______several lines of data in parallel. The research was carried out by the Ultra Parallel Visible Light Communications project, and funded by the Engineering and Physical Sciences Research Council.
    Existing LED light bulbs could be【C14】______to transmit Li-Fi signals with a single microchip, and the technology would also be of use in situations where radio frequencies cannot be used for fear of【C15】______with electronic circuit. And although Li-Fi bulbs would have to be kept on to transmit data, the bulbs could be【C16】______to the point that they were not visible to humans and yet still【C17】______. One draw-back is that the data receiver would have to be in sight of the transmitter-bulb as visible light does not【C18】______solid materials.
    The makers of Li-Fi note that this quality might actually be an advantage in some【C19】______making Li-Fi more【C20】______than Wi-Fi with hackers unable to access unsecured internet connections from out of sight of the transmitter.
【C1】
选项 A、subsequently
B、presently
C、lately
D、previously
答案D
解析 本句提到Li-Fi的最快传输速度是3Gbit／s，今年早些时候(earlier this year)在德国测得。D项previously“以前”与earlier对应，故正确。该词也与本句谓语动词所使用的一般过去时(文章整体使用一般现在时)构成正确语法搭配。
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