2. 外语
  3. What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器). Almost everyone has

What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器). Almost everyone has

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问题     What do cats’ eyes and highway reflector signs have in common? They both act as retro-reflectors(反响反射器).
    Almost everyone has noticed the frightening appearance of animals at night, as their eyes seem to glow in reflected light. One may think that just as reflective highway signs alert the motorists to many road hazards, so early man was often warned of danger by light from his campfire reflected in the eyes of lurking(潜伏)predators. In both cases, the light is ret-roreflected, giving it a particularly bright appearance.
    The principles of retroreflection have been understood for centuries. However, it is only within the last fifty or sixty years, with the wide use of the automobile, that this area of optics(光学)has received important commercial application. Today, the uses of retroreflective materials are many. They are applied to bicycles and motor vehicles to make them more visible at night. And they assist pilots by improving the visibility of runway markers.
    Large sums are spent for retroreflective materials, but purchasers have often found it difficult to specify performance for the materials they buy. Performance is of concern not only from the standpoint of the brightness of reflected light, but also from the standpoint of its color. It is important, for example, that the yellow hues(色调)in warning signals be of consistent color quality on all road signs so the driver can rely on color, as well as shape, to discern the signs’ meanings. Seven colors — silver, blue, yellow, red, green, brown and orange — are currently used for marking the interstate highway system.
This passage is primarily concerned with______.
选项 A、technology in photoelectric cells
B、retroreflection in animals and insects
C、natural and man-made retroreflection
D、specific performance of retroreflective materials
答案C
解析 本题属于主旨大意题，提问的是本文主要讲述的什么。通观全文。前两段谈论了动物的眼睛和公路反光标志牌的共同之处(都起到对光进行反向反射的作用)；后三段则围绕反向反射材料展开。由此可见，文章主要是以光的天然和人工反向反射为话题的。故选C)。
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