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  3. Every April, along with many other species of birds, the swallow arrives to

Every April, along with many other species of birds, the swallow arrives to

游客2024-08-13  58
问题     Every April, along with many other species of birds, the swallow arrives to spend the summer months in northern Europe, Iran and parts of Russia’s Siberia. Here it will breed and raise its young.
      The swallow is well known for several reasons. Firstly, it is very distinctive, with its forked tail and characteristic acrobatic swooping flight. Secondly, it is very common, and, like its near relative the   house martin, lives in close proximity to human habitation, at least in rural areas. 【B1】_________

    For centuries, people have observed swallows, and noted their arrival and their patterns of feeding. 【B2】_________ In England, people comment on unpredictable late spring weather by saying, "One swallow does not make a summer." Similarly, "The swallows are flying low" was held to predict rainy, even stormy weather.
    【B3】__________Insects keep low in these conditions, so do swallows that hunt them. At the end of the summer season, when swallows are about to leave, they frequently flock together in large numbers.  When people remark that swallows are gathering, they mean the autumn has arrived.
    At some point in mid-September swallows leave together, usually all on the same day. One day there are thousands, the next there are none, and none will be seen again until the following spring. For centuries, this was a complete mystery to people. The Hampshire naturalist Gilbert White, writing in the late eighteenth century, believed that swallows dived into ponds and rivers in autumn and remained in the bottom mud the whole winter, re-emerging the following spring. This idea seems extraordinary to us, but White was not a stupid man: many of his other observations of natural life were informed and accurate. 【B4】_________The idea that swallows migrate to central or southern Africa would have seemed as fanciful to him as his theory seems to us.
    Although we now know that swallows migrate, there are still unanswered questions.  Why do they go so far? Why not stay on the shores of the Mediterranean? The majority continue to equatorial Africa, and some even further south. 【B5】_________ Those from France, Germany and much of western Europe have mostly been traced to East Africa, Kenya or Tanzania, for example. Above all, how does a bird weighing approximately twenty grams find its way across mountain ranges, ocean and desert to winter in the south, and then return the following year to the very location it was born, in some cases to the very same nest?
    Complete the passage with the following sentences. There are two extra sentences that you do not need to use.
    A.  In several countries, these observations have passed into the language as proverbs or sayings.
    B.  In this case, however, he simply had no means of determining the truth and was forced to make a random guess.
    C. There may be some truth in this observation, though it is the insects the swallows feed on that seem to be more susceptible to the fall in barometric pressure that heralds a storm.
    D.  Also it appears that populations of swallows that have bred in different countries also spend the winter in different areas.
    E.  By these means, they travel quite long distances.
    F.  It is, however, rarely to be encountered in towns or cities.
    G.  Exhausted swallows sometimes come to rest on ships way out in the Atlantic Ocean. [br] 【B3】
选项
答案 C
解析 空格后一句提到昆虫在这种情况下保持低飞，昆虫的捕食者燕子也飞得很低。结合选项可知，选项C(这一观察结果可能有些道理，尽管燕子所食的昆虫似乎更容易受到预示暴风雨来临的气压下降的影响)与下文衔接紧密，故答案为C。
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