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  3. It was previously believed that dinosaurs were cold-blooded creatures, like reptiles. However, a recent discovery has lad resear

It was previously believed that dinosaurs were cold-blooded creatures, like reptiles. However, a recent discovery has lad resear

admin2010-04-12  45
问题     It was previously believed that dinosaurs were cold-blooded creatures, like reptiles. However, a recent discovery has lad researchers to believe they may have been warm- blooded. The fossilized remains of a 66 million-year-old dinosaur’s heart were discovered and examined by x-ray. The basis for the analysis that they were warm- blooded is the number of chambers in the heart as well as the existence of a single aorta (主动脉).
    Most reptiles have three chambers in their hearts, although some do have four. But these that have four chambers, such as the crocodile, have two arteries (动脉) to mix the oxygen-heavy blood with oxygen-lean blood. Reptiles are cold-blooded, meaning that they are dependent on the environment for body heat. Yet the fossilized heart had four chambers in the heart as well as a single aorta. The single aorta means that the oxygen-rich blood was completely separated from the oxygen-poor blood and sent through the aorta to all parts of the body.
    Mammals, on the other hand, me warm-blooded, meaning that they generate their own body heat end are thus mere tolerant of temperature extremes. Birds and mammals, because they are warm blooded, move more swiftly and have greater physical endurance than reptiles.
    Scientists believe that the evidence now points to the idea that all dinosaurs were actually warm- blooded. Ironically, the particular dinosaur in which the discovery was made was a Tescelosaurus, which translates to "marvelous lizard." A lizard, of course, is a reptile.
The author implies that birds ______.
选项 A、move faster and have greater endurance than reptiles
B、move slower and have less endurance than reptiles
C、move faster and have greater endurance than dinosaurs
D、move slower and have less endurance than dinosaurs
答案A
解析 根据第三段最后一句话“Birds and mammals，because they are warm blooded，move more swiftly and have greater physical endurance than reptiles，”鸟类和哺乳动物是恒温的，所以与爬行动物相比，它们移动的速度更敏捷，同时身体的忍耐力更强。只有A符合文中说法。
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