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双绞线电缆的外部护套上每隔3英尺（1英尺=0.3048米）会印刷上一些标识
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光纤传光原理就是利用了纤芯与包层的界面上发生的全内反射来传播光波的。
On 20 November 1984, ________sailed from Shanghai, arriving in Antarctica on 25 December, marking a significant progress in China's polar research.
________is China's first space station which serves as both a manned laboratory and an experimental testbed. It demonstrates its orbital rendezvous and docking capabilities.
________ 's pioneering work in hybrid rice breeding and production techniques has revolutionised rice cultivation in China and established China's world leading position in hybrid rice research.
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