Hitherto, there is no evidence yet that would definitively prove whet

游客2024-01-11 18

问题          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
(5)    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
(10) 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
(15) almost impossible level of preservation over 65 million years, plus the advent of
   biotechnology that does not yet exist. [br] According to the passage, the most severe problem currently facing scientists in conclusively determining whether certain dinosaurs were warm-blooded is

选项 A、proving that thermoregulation is the primary means by which metabolic rates are influenced
B、developing a way of distinguishing between oxygen 18 and oxygen 16
C、showing that an absence of seasonal variation in oxygen 16 implies a constant internal temperature
D、finding a sample of dinosaur tissue which has survived 65 million years in a relatively intact form
E、determining which species of dinosaurs were most likely to be warm-blooded, and focusing research there

答案 D

解析

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