GRE考试

【单选题】Hitherto, there is no evidence yet that would definitively prove whether or not some dinosaurs were warm-blooded, but scientists have begun to investigate　oxygen isotopic abundances in the annual growth bands of teeth or bones of high Line latitude, hence seasonally influenced, terrestrial dinosaurs. The ratio of oxygen isotopes depends on temperature, and an absence of seasonal variations in oxygen 18―a heavy version of the common oxygen 16 atom―would　strongly suggest that the animals maintained a constant internal　temperatures. Such a finding would not, however, constitute "proof"　that dinosaurs were warm blooded, as there are external mechanisms that cold-blooded animals employ to　regulate body temperatures and thereby influence metabolic rates. More nettlesome is that proof would have to come from discovery of intact dinosaur remains in which the soft tissue had not been replaced or altered, and from which the biomolecules responsible for thermoregulation could be extracted identified and characterizeD、Such a proof is unlikely, as it would require an　almost impossible level of preservation over 65 million years, plus the advent of biotechnology that does not yet exist. The passage suggests which of the following about the hypothetical discovery of an absence of seasonal variations in oxygen 18 molecules 　　Ⅰ. It would not prove that certain dinosaurs were capable of regulating their temperatures internally.　　Ⅱ. One likely source of such a discovery would come from annual growth bands of dinosaur teeth.　　Ⅲ. The fact that no biotechnology yet exists to elucidate thermoregulation biochemistry proves such a discovery is impossible.　　Ⅳ. The discovery would be profound, because oxygen 18 is only found in fossil records where there is seasonal variation.
A、Ⅰ and Ⅱ only
B．Ⅱ and Ⅲ only
C．Ⅲ and Ⅳ only
D．Ⅰand Ⅳ only
E．Ⅱ, Ⅲ, and Ⅳ only

网考网参考答案：A
网考网解析：
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