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 Scientists studying the physiology 
 of dinosaurs have long debated whether 
 dinosaurs were warm- or cold-blooded. 
 Line  Those who suspect they were warm- 
 (5)   blooded point out that dinosaur bone 
 is generally fibro-lamellar in nature; 
 because fibro-lamellar bone is formed 
 quickly, the bone fibrils, or filaments, are 
 laid down haphazardly. Consistent with 
 (10)  their rapid growth rate, warm-blooded 
 animals, such as birds and mammals, 
 tend to produce fibro-lamellar bone, 
 whereas reptiles, which are slowgrowing 
 and cold-blooded, generally 
 (15)  produce bone in which fibrils are laid 
 down parallel to each other. Moreover, 
 like the bone of birds and mammals, 
 dinosaur bone tends to be highly 
 vascularized, or filled with blood 
 (20)  vessels. These characteristics, 
 first recognized in the 1930’s, 
 were documented in the 1960’s by 
 de Ricqlès, who found highly vascularized, 
 fibro-lamellar bone in several 
 (25)  groups of dinosaurs. In the 1970’s, 
 Bakker cited these characteristics as 
 evidence for the warm-bloodedness of 
 dinosaurs. Although de Ricqlès urged 
 caution, arguing for an intermediate type 
 (30)  of dinosaur physiology, a generation of 
 paleontologists has come to believe 
 that dinosaur bone is mammalianlike. 
 In the 1980’s, however, Bakker’s 
 contention began to be questioned, as a 
 (35)  number of scientists found growth rings 
 in the bones of various dinosaurs that 
 are much like those in modern reptiles. 
 Bone growth in reptiles is periodic in 
 nature, producing a series of concentric 
 (40)  rings in the bone, not unlike the growth 
 rings of a tree. Recently, Chinsamy 
 investigated the bones of two dinosaurs 
 from the early Jurassic period 
 (208-187 million years ago), and found 
 (45)  that these bones also had growth rings; 
 however, they were also partially fibrolamellar 
 in nature. Chinsamy’s work 
 raises a question central to the debate 
 over dinosaur physiology: did dino- 
 (50)  saurs form fibro-lamellar bone because 
 of an innately high metabolic rate associated 
 with warm-bloodedness or 
 because of periods of unusually fast 
 growth that occurred under favorable 
 (55)  environmental conditions? (Although 
 modern reptiles generally do not form 
 fibro-lamellar bone, juvenile crocodiles 
 raised under optimal environmental 
 conditions do.) This question remains 
 (60)  unanswered; indeed, taking all the evidence 
 into account, one cannot make 
 a definitive statement about dinosaur 
 physiology on the basis of dinosaur 
 bone. It may be that dinosaurs had an 
 (65) intermediate pattern of bone structure 
 because their physiology was neither 
 typically reptilian, mammalian, nor avian. 
 
 The author of the passage mentions bone growth patterns in juvenile crocodiles most 
 likely in order to 
 A. provide support for the argument that reptiles are not related to dinosaurs 
 B. undermine the claim that most reptiles are slow-growing 
 C. offer an explanation as to why juvenile crocodiles differ from most modern 
 reptiles 
 D. suggest the juvenile crocodiles have a type of physiology intermediate between 
 that of mammals and that of reptiles 
 E. suggest that the presence of fibro-lamellar bone does not resolve the debate over 
 请教,我实在不知道怎样推出E答案(正确答案给的是E),我没思路,或许是没看懂 
 谢谢  |