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.
It could be concluded from the passage that______.
选项 A、retroreflective materials give off light in the dark
B、retroreflective paint can be purchased at most hardware stores
C、it is sometimes difficult for purchasers to decide the right kind of retroreflective materials to buy
D、people prefer to use yellow color as warning signals on highways
答案C
解析 本题为推理判断题。依据是第四段第一句“…purchasers have often found it difficult to specify performance for the materials they buy”，既然购买者发现难以明确地说出他们要购买的反向反射材料的性能，说明他们在做出选择的时候要颇费一番周折。因此，答案应为C)。
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