Question

阅读理解。

Contrary to people's previous knowledge, it's food shortage not dietary preference that motivates birds to migrate thousands of miles back and forth between breeding and non­breeding areas each year, a new research shows.

“It's not whether you eat insects，fruits or candy bars or where you eat them that counts，but how reliable that day­to­day food source is，” said the study leader W．Alice Boyle of the University of Arizona.

To figure out the underlying pressure that drives some birds to leave home for the season，Boyle examined 379 related species of New World flycatchers(捕蝇鸟) and compared their sizes，food types, habitats, migratory behaviors and whether or not they fed in flocks.

To compare the birds，the researchers constructed a “supertree”  showing the exact evolutionary relationships among different species.

A computer analysis then determined whether a particular species was migratory because it ran in the “family” or whether something in the bird's environment was forcing it to leave each season.Boyle and her colleagues found that food shortage was the number one issue that predicted a species' migratory behavior. “Food availability is the underlying pressure, not diet and habitat，” Boyle said.

An alternative strategy that the birds use to handle food shortage is to hunt in flocks, since a group is more likely to find a new source of food than an individual.

“If you suffer from food shortage, you have two options，” Boyle said.“You can either hunt with other birds or you can migrate.”

1.Birds were thought to migrate in order to ________.

A．seek their favorite food in a new place

B．avoid being constantly hunted

C．breed more young in a new place

D．adjust themselves to the changes of weather

2.What is Paragraphs 3 and 4 mainly about?

A．The aim of the research.

B．The basis of the research.

C．The process of the research.

D．The findings of the research.

3.The passage implies that ________.

A．the birds' food sources are getting rare in the world

B．the living surroundings are severe for birds

C．birds search for food separately

D．birds can survive only by hunting in flocks

4.For what purpose does the author write the text?

A．Educating readers.

B．Informing readers.

C．Drawing people's attention.

D．Condemning the bad environment.

Answer

1.A

2.C

3.A

4.B

【解析】

试题分析：

1.细节理解题。根据第一段第一句中“Contrary to people's previous knowledge, it's food shortage not dietary preference that motivates birds to migrate”可知，是食物的短缺而不是对食物的偏好驱使鸟类迁徙，这一新的研究结果推翻了人们过去错误的观点，即人们过去认为：是对食物的偏爱驱使鸟类迁徙。故选A项。

2.段落大意题。根据第三段中“examined 379 related species of New World flycatchers(捕蝇鸟)”和“compared their sizes，food types，habitats，migratory...”可知，第三段介绍了采集样本、对比样本的过程。根据第四段中“constructed a ‘supertree’ showing...”可知，第四段介绍了研究方法。由此可知，第三、四两段综合说明了此项研究是如何进行的。故选C项。

3.推理判断题。根据文章第一句“...it's food shortage not dietary preference that motivates birds to migrate thousands of miles back and forth...”可知，是食物的短缺而不是对食物的偏好驱使鸟类迁徙。由此可推知，世界上鸟类的食物资源正在减少。故选A项。

4.写作意图题。文章从第一段提出重大发现到后面几段叙述研究过程，再到最后一段的研究结论可知，本文的写作目的是告知读者这一研究的新发现。故选B项。