题目

Scientists have never known for sure whether dinosaurs were warm-blooded animals, like mammals and birds, or cold-blooded, like reptiles and fish. A recent study shows that in fact many dinosaurs might not have belonged to either category but instead have fallen somewhere in the middle. Warm-blooded animals have bodies that are able to make their own heat. Their body temperatures stay about the same whether it is hot or cold outside. Cold-blooded animals can not make their own heat, so their body temperatures depend on how warm the outside temperature is. Warm-blooded animals have much more active lifestyles than cold-blooded ones. When scientists first discovered the bones of ancient dinosaurs in the 1800s, they were sure the huge creatures must have been slow. But as scientists found more bones of smaller, quicker dinosaurs, like Velociraptor, they realized that the creatures may have been much more active than they had thought. A team of biologists began to examine. They knew that warm-blooded animals grow faster than cold-blooded ones. The researcher realized that they could determine whether a dinosaur had been warm-or cold-blooded by finding its growth rate. The scientists examine the growth rings in bones from 21 different dinosaur species. The width of the growth rings showed how much the dinosaurs grew each year, much like the rings in the tree trunk do. “Our results showed that dinosaurs had growth rates that were actually not characteristic of warm-blooded or cold-blooded animals,” said Brian Enquist, a scientist on the research team. “They didn’t act like mammals or birds, nor did they act like reptiles or fish.” Instead, dinosaurs fell somewhere in between. Scientists called the middle-of-the-road creatures “mesotherms”. Being mesotherms gave dinosaurs many advantages. They were faster and stronger than reptiles that had to rely on the sun for warmth. Being somewhat cold-blooded had its benefits too. Cold-blooded animals bum energy more slowly. So they need much less food to live than warm-blooded animals. “It is doubtful that a lion size of T-rex could eat enough to survive,” explains John Grady, another biologist on the research team. By being mesothermic, the dinosaurs could be both fast and big. 12. What is Paragraph 2 mainly about? A. The advantage of cold-blooded animals.     B. The disadvantages of warm-blooded animals.     C. The differences between warm-and cold-blooded animals.     D. The advantages of both warm-and cold-blooded animals. 13. It can be inferred that mesotherms grow _______.     A. as slowly as cold-blooded animals      B. as fast as warm-blooded animals     C. slower than cold-blooded animals      D. slower than warm-blooded animals 14. A lion is mentioned in the last paragraph to stress that ________.     A. dinonsaurs moved very fast           B. dinonaurs are large animals     C. dinosaurs needed less food to survive   D. dinosaurs had to rely on the sun for warmth 15. The text is mainly about ________.     A. how dinosaurs disappeared     B. the growth areas of dinosaurs     C. the appearance and behavior of dinosaurs     D. if dinosaurs were warm-or cold-blooded animals 答案：CDCD

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