A
Meet the longestliving vertebrate(脊椎动物)in the world, the Greenland shark.
Found primarily in the very cold waters of the North Atlantic, these slowswimming sharks can be as big as the largest great whites, reaching up to 21 feet in length.They're among the largest of carnivorous (食肉的) fish, and yet grow perhaps only a centimeter or so a year.Such slow growth yet big size is usually an indicator of a longlived animal.
“We only expected that the sharks might be very old，” Julius Nielsen, at the University of Copenhagen in Denmark, told NPR.“But we did not know in advance.And it was, of course, a very big surprise to learn that it was actually the oldest vertebrate animal.”
Imagine being 150 years old before you're ready to have your first child! Imagine being born before the United States was even a reality.For humans — who rarely make it to a century mark — it's difficult to fully understand.
Little is known about Greenland sharks, even basics such as where they give birth or how many of them there are, though researchers at a conference at the University of Exeter thought that they may mate in “hidden”Arctic fjords.No one has even witnessed one hunting, though they have been found to have various vertebrate ones in their stomachs such as polar bear, seals, fastswimming fish and even moose etc.
Given the shark's incredibly long lifespans, scientists are diving into the sea creature's genome, looking for clues.That conference also highlighted the work being done to separate the shark's longevity gene, with complete DNA information gathered from almost 100 sharks, including some born in the 1750s.Finding such a gene could go a long way in explaining why some vertebrates, like humans, have such limited lifespans.
These sharks also serve as swimming history books.Their tissue, bones and DNA could tell us a great deal about the waters of the world from a time before the Industrial Revolution, largescale commercial fishing and the pronounced ocean pollution we see today.
Check out what it's like to swim with one in this encounter with what is a small and young — and yet to us, still fairly old — Greenland shark.
语篇解读：本文是一篇说明文。科学家们发现格陵兰鲨鱼是世界上最长寿的脊椎动物。
1．What can we know about Greenland sharks from the first two paragraphs?
A．Longestliving, and slowswimming carnivorous vertebrate.
B．Longestliving, and slowestswimming vertebrate.
C．Largest, but fastgrowing carnivorous vertebrate.
D．Longestliving, largest carnivorous vertebrate but fastgrowing.
解析：选A 细节理解题。根据第一段可知，格陵兰鲨鱼是世界上最长寿的脊椎动物。根据第二段第一、二句可知，这种鲨鱼游泳缓慢并且食肉。
2．Why were scientists surprised after they examined Greenland shark?
A．Greenland shark can live as old as humans.
B．Greenland shark is the largest animal in the world.
C．Greenland shark can live more than one hundred years.
D．Greenland shark is really the oldest vertebrate in the world.
解析：选D 细节理解题。根据第三段中的“a very big surprise to learn that it was actually the oldest vertebrate animal”可知，科学家们因为发现格陵兰鲨鱼是世界上最古老的脊椎动物而感到惊讶。
3．What kind of animals do Greenland sharks prefer?
A．Both polar bear and seal.
B．Only fastswimming fish.
C．Various vertebrate animals.
D．Polar bear, moose and fish.
解析：选C 细节理解题。根据第五段最后一句可知，格陵兰鲨鱼喜欢吃各种各样的脊椎动物。
4．What information can we get from the passage?
A．Scientists declare that they have known all about Greenland sharks.
B．Scientists want to get more information about longevity from their study on sharks.
C．Scientists consider sharks can only serve as swimming history books.
D．Scientists just want to know why Greenland sharks have a long life.
解析：选B 推理判断题。根据第六段可推知，科学家们希望从他们对鲨鱼的研究中获得更多关于长寿的信息。
