2. 外语
  3. To many web-building spiders, most of【C1】______ are nearly blind, the web is their essential window【C2】______ the world., their

To many web-building spiders, most of【C1】______ are nearly blind, the web is their essential window【C2】______ the world., their

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问题      To many web-building spiders, most of【C1】______ are nearly blind, the web is their essential window【C2】______ the world., their means of communicating,【C3】______ prey, meeting mates and protecting themselves. A web-building spider【C4】______ its web is like a man marooned on an island of solid rock, totally out of touch and destined to starve to death. So【C5】______ is the web to an orb-web spider’s survival that the animal will continue to construct new webs daily【C6】______ it is being starved.
     For 16 days the【C7】______ spider builds completely normal webs. Then, as the animal gets scrawnier, it constructs a wider-meshed web using【C8】______ strands. Such webs would only trap larger prey, which is more【C9】______ from the perspective of a starving spider.
     The spider【C10】______  energy by recycling web protein. It simply eats its own web each evening and re-uses it to manufacture【C11】______ silk. In studies with radioactively labeled materials, it【C12】______ that 95 percent of web protein reappeared in【C13】______ web. Most of the energy needed for web-building is used in walking over the strands as they are laid down.
     Scientists are【C14】______ by the adaptability of the spider’s highly preprogrammed brain, which is larger【C15】______ its size than the brain of any other invertebrate. If web-building is interrupted, or if some of the【C16】 ______ strands are destroyed, the spider【C17】______ retraces its steps to see where the web is【C18】______ and then finishes building a【C19】______ web. One spider will even finish building the incomplete web of【C20】______ .
【C12】
选项 A、was found
B、found
C、has found
D、had found
答案A
解析 此题考查被动语态。首先，根据形式主语判断出这里应该使用被动语态。其次，从句首的In studies with radioactively labeled materials以及后面的reappeared可以看出，应该使用过去式。因此，A项符合题意。
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