题目内容：

Bats are the only mammals that can fly a great distance, but they have another ability. Many bats live a very long time for an animal their size.

European researchers are studying bats to understand why they live so long. They hope to make discoveries to fight the aging process (过程) in human beings.

Last week, the group of scientists said they had found important biological qualities in some bat species. The group studied bat chromosomes (染 色 体), a line of genes found in the nucleus(核) ofcells. The scientists were most interested in parts connected to the ends of the chromosomes. They are called telomeres(端 粒). Telomeres protect the ends of chromosomes, which shorten each time a cell divides. Scientists believe this shortening process causes cells to break down.            .

A report on bats was published this month in the journal Science Advances.

Among the leaders of the study was Emma Teeling, a biologist with University College Dublin in Ireland. Teeling said studying long-living mammals that have developed ways to fight aging “is another way to prove the molecular(分 子) basis of extended ‘health length.’” She added that studying bats made scientists able to learn more about the processes “that drive healthy aging.”

The European researchers studied 493 bats from four bat species. The group used information that had been gathered over more than 60 years. Of these animals, the greater mouse-eared bat generally lived the longest, an average of 37 years.

The scientists said this and a related species, which are grouped together under the name Myotis, had telomeres that did not shorten with age. Another Myotis bat holds the record for oldest age, reaching 41 years.

The scientists’ findings suggest that these bats’ cells have the ability to keep and repair their telomeres. This, they said, helps guard against the aging process. Based on its body size, a bat like the greater mouse-eared bat would be expected to live four years. But, these mammals have been found to live nearly 10 times longer than that.

The scientists found that Eighteen of these are bats. The only exception is an unusual African rodent, the naked mole rat.

1.Which sentence can be put at the end of Paragraph 3?

A. This makes scientists able to study bats.

B. That’s why bats can fly a great distance.

C. They say this is what causes aging.

D. They discover the cells connected to humans.

2.Why do some species of bats live a very long time?

A. Because they have a line of long-living genes out of the cells.

B. Because their cells have the ability to keep and repair their telomeres.

C. Because they have another ability to live longer without any food or water.

D. Because telomeres protect the ends of chromosomes to stop cells dividing.

3.The underlined word “that” refers to      .

A. four years    B. body size    C. the aging process    D. the ability to repair

4.What’s the best title of the passage?

A. Differences Between Long-Living Animals

B. A Science Report on Chromosomes

C. Do Bats Hold the Secret to Long Life?

D. Are Humans and Bats Similar in Protecting Themselves?