Passenger pigeons(旅鴿) once flew over much of the United States in unbelievable numbers. Written accounts from the 18th and 19th centuries described flocks(群) so large that they darkened the sky for hours.

It was calculated that when its population reached its highest point，there were more than 3 billion passenger pigeons—a number equal to 24 to 40 per cent of the total bird population in the United States, making it perhaps the most abundant bird in the world. Even as late as 1870 when their numbers had already become smaller, a flock believed to be 1 mile wide and 320 miles (about 515 kilometres) long was seen near Cincinnati.

Sadly, the abundance of passenger pigeons may have been their undoing. Where the birds were most abundant, people believed there was an ever­lasting supply and killed them by the thousands. Commercial hunters attracted them to small clearings with grain, waited until pigeons had settled to feed, then threw large nets over them, taking hundreds at a time. The birds were shipped to large cities and sold in restaurants.

By the closing decades of the 19th century, the hardwood forests where passenger pigeons nested had been damaged by Americans' need for wood, which scattered(驅(qū)散) the flocks and forced the birds to go farther north, where cold temperatures and spring storms contributed to their decline. Soon the great flocks were gone, never to be seen again.

In 1897, the state of Michigan passed a law prohibiting the killing of passenger pigeons, but by then, no sizable flocks had been seen in the state for 10 years. The last confirmed wild pigeon in the United States was shot by a boy in Pike County, Ohio, in 1900. For a time, a few birds survived under human care. The last of them, known affectionately as Martha, died at the Cincinnati Zoological Garden on September 1, 1914.

24. In the 18th and early 19th centuries, passenger pigeons ________.

A. were the biggest bird in the world

B. lived mainly in the south of America

C. did great harm to the natural environment

D. were the largest bird population in the US

25. The underlined word “undoing” probably refers to the pigeons' “________”.

A. escape　　　　　　　B. ruin

C. liberation D. evolution

26. What was the main reason for people to kill passenger pigeons?

A. To seek pleasure.

B. To save other birds.

C. To make money.

D. To protect crops.

27. What can we infer about the law passed in Michigan?

A. It was ignored by the public.

B. It was declared too late.

C. It was unfair.

D. It was strict.

【要點綜述】 本文敘述了旅鴿逐漸消失的過程。在美國，18世紀和19世紀旅鴿的數(shù)量很多。人們認為旅鴿數(shù)量多，會有永久的供應(yīng)，于是殺害了成千上萬的旅鴿。而在19世紀末，美國人伐木驅(qū)散了旅鴿。1897年密歇根州通過禁止屠殺旅鴿的法律時，在該州已經(jīng)10年沒有見過大的旅鴿群了。最后一只旅鴿于1914年在辛辛那提動物園死去。

24. D　細節(jié)理解題。根據(jù)第二段中的“…a number equal to 24 to 40 per cent of the total bird population in the United States…”可知選D。

25. B　詞義猜測題。根據(jù)第三段中的“Where the birds were most abundant, people believed there was an ever­lasting supply and killed them by the thousands.”可知，人們認為旅鴿數(shù)量多，會有永久的供應(yīng)，于是殺害了成千上萬的旅鴿。由此判斷undoing的意思是“死亡，毀滅”。故選B。

26. C　推理判斷題。根據(jù)第三段中的“Commercial hunters attracted them to small clearings with grain, waited until pigeons had settled to feed, then threw large nets over them, taking hundreds at a time. The birds were shipped to large cities and sold in restaurants.”可知，人們殺死旅鴿主要是為了賺錢。故選C。

27. B　推理判斷題。根據(jù)最后一段中的“In 1897, the state of Michigan passed a law prohibiting the killing of passenger pigeons, but by then, no sizable flocks had been seen in the state for 10 years.”可知，在密歇根州通過禁止屠殺旅鴿的法律時，在該州已經(jīng)10年沒有見過大的旅鴿群了，由此可推斷旅鴿的數(shù)量已經(jīng)很少了，因此這項法律通過得太晚了。故選B。