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The now extinct passenger pigeon has the dubious honor of being the last species anyone ever expected to disappear. At one point, there were more passenger pigeons than any other species of bird. Rough【C1】________of their population went as high as five billion and they accounted for around 40 percent of the total indigenous bird population of North America in the early 19th century. Despite their huge population, passenger pigeons were【C2】________to human intrusion into their nesting territory. Their nests were shabby things and two weeks after the eggs【C3】________. the parent pigeons would abandon their offspring, leaving them to take care of themselves. People discovered that these baby pigeons were really tasty, and the adult birds were also quite【C4】________. First the Native Americans and then the transplanted Europeans came to consider the birds a great【C5】________. By the 1850s, commercial trapping of passenger pigeons was proceeding at an【C6】________pace. Hundreds of thousands of the birds were being harvested every day to be made into popular pigeon pies. In addition, large【C7】________of the pigeons’ nesting territory were being cleared away for planting crops and creating pasture land. As numerous as the passenger pigeons were, they were not an【C8】________resource. By the 1880s, it was noticed that the bird population had become seriously【C9】________. The last passenger pigeons killed in the wild were shot in 1899. Eventually those billions and billions of birds shrank to a single remaining【C10】________. a passenger pigeon named Martha, who died on September 1, 1914, in captivity at the Cincinnati Zoo. In addition to being the end of an era, it was also the first time humans were able to exactly time the extinction of a species. A) vulnerable F) refuge K) excerpts B) unprecedented G) plazas L) estimates C) tracts H) infinite M) edible D) specimen I) hatched N) depleted E) robust J) expired O) delicacy
问答题
【C1】
【正确答案】L
【答案解析】空格前为形容词Rough，空格后为介词短语of their population，由此可知，空格处应填入一个被形容词Rough修饰的名词。由本句中的went as high as five billion可知，这里在讲述旅鸽的数量，而由于数量众多(高达50亿) ，因此这一数量只能是估算出来的数量，故estimates符合语境。
问答题
【C2】
【正确答案】A
【答案解析】空格前是系动词were，空格后是介词短语to human intrusion，由此可知，本空应填入一个形容词，构成be+adj. +to sth.的结构。由句首表示让步关系的介词短语Despite their huge population(尽管旅鸽数量庞大和文章后面提到的旅鸽因人们捕杀而灭绝的内容可知，这里是说“旅鸽的筑巢区域易遭受人类入侵”，be vulnerable to为固定短语，意为“易受到……的伤害”，符合语境，故应填入vulnerable。
问答题
【C3】
【正确答案】I
【答案解析】空格前为two weeks after the eggs，空格后为逗号，由此可知，此处是after引导的时间状语从句，缺少谓语动词，此处描述过去发生的事情，故应使用一般过去时。由主句the parent pigeons would abandon their offspring，leaving them to take care of themselves(亲鸽会抛弃它们的后代，让它们自己照顾自己) 可知，从句应该说的是旅鸽蛋“孵化”两周后……，故hatched符合语境。
问答题
【C4】
【正确答案】M
【答案解析】空格前为were also quite，空格后为句点，由此可知，空格处应填入一个形容词，充当系动词were的表语，同时被副词quite所修饰。由前面的并列分词these baby pigeons were really tasty(这些幼鸽很美味) 可知，and后接的并列句the adult birds were also quite________说的是成年鸽的味道，前后为并列关系，故空格处应填入与tasty(美味的) 意思相近的形容词，备选项中edible符合语境。
问答题
【C5】
【正确答案】O
【答案解析】空格前为不定式短语to consider the birds a great，空格后为句点，由此可知，空格处应填入一个名词，被形容词great修饰，充当宾语birds的补足语。由前两空的分析可知，人们发现幼年旅鸽和成年旅鸽都很好吃，那么本句承接上文，具体说哪些人开始食用旅鸽，根据此处语境“首先是美洲原住民，然后是移居的欧洲人，都开始把这种鸟视为________”可知，备选名词中delicacy能够衔接上文。
【答案解析】空格前为形容词large，空格后为介词短语of the pigeons’ nesting territory，由此可知，空格处应填入一个被形容词large修饰的名词，同时这个名词被后置的of介词短语所修饰。根据此处语境“此外，旅鸽筑巢区域的大片________被清理出来，用于种植庄稼和开辟牧场”可知，备选项中tracts符合题意，large／vast tracts of为固定短语，意为“大片的……”。
问答题
【C8】
【正确答案】H
【答案解析】空格前为不定冠词an。空格后为名词resource，由此可知，空格处应填入一个形容词或分词，充当resource的定语。As numerous as the passenger pigeons were意为“尽管旅鸽数量众多”，表示让步关系，可知主句是说“但它们并不是无穷无尽的资源”，故infinite符合语境。
问答题
【C9】
【正确答案】N
【答案解析】空格前为had become seriously。空格后为句点，故可知，空格处应填入形容词或分词，充当连系动词become的表语。上文提到旅鸽因美味可口而被人们大量捕杀，下一句指出“最后一批在野外被杀死的旅鸽是在1899年被射杀的”，由此可知，此处是说“到了19世纪80年代，人们注意到旅鸽的数量已经严重减少”，故depleted符合语境。
问答题
【C10】
【正确答案】D
【答案解析】空格前为shrank to a single remaining，空格后为逗号，由此可知，空格处应填入一个名词，被不定冠词a、形容词single和remaining所修饰。由下文a passenger pigeon named Martha, who died on September 1, 1914, in captivity at the Cincinnati Zoo (一只名叫玛莎的旅鸽，于1914年9月1日在辛辛那提动物园的圈养中去世) 可知，旅鸽只剩下动物园里唯一的一只，故specimen符合语境。