【正确答案】 B

【答案解析】 [听力原文]
   Good morning, everyone. I feel it a great honor to be invited to give a talk on dinosaurs, which I chose to study as my life career at an early age. Our young students are often fascinated with dinosaurs because they are real gigantic monsters. They are nature's best special effects, produced by evolution. But, what exactly are dinosaurs? Well, when dinosaurs were first dug up in the mid-1800's, paleontologists recognized right away that these extinct animals on one hand looked like crocodiles, but also looked like rhinos or elephants and also like birds. This three-way comparison was made right away. It was a weak consensus they ought to be called reptiles. Nevertheless, paleontologists recognized that dinosaurs had many birdlike characteristics, and by 1860, most scholars accepted birds as living dinosaurs. Then between 1920 and 1940, scholars came to view dinosaurs as being cold-blooded, gray, boring animals. However, there was no evidence for it. There was no definitive scientific paper proving that. I myself had questioned this view when I was a college student.
   Dinosaurs reigned on Earth for 165 million years. During that time, there were warm-blooded mammals alive, tiny little fur balls. Now does it make sense that cold-blooded, stupid animals would reign while intelligent warm-blooded animals would have stayed small? No. The dinosaurs kept on winning because they must have been fundamentally better than those little furry mammals. This made me wonder if dinosaurs were in fact warm-blooded animals. So I started to dig up relevant evidence.
   The first thing I did was to review history. I summarized the fossil history of dinosaurs and found that, for 165 million years on land, all meat eaters or plant eaters bigger than 10 pounds were dinosaurs. There was wave after wave of evolutions, extinctions, and evolutions. Every time, the big meat eaters and plant eaters that emerged were dinosaurs—different kinds of dinosaurs, but they were dinosaurs. The fact that the dinosaurs won over mammals again and again proved they were superior to mammals. In a paper I wrote called "The Superiority of Dinosaurs", I pointed out that the limbs of dinosaurs are not like those of a lizard, frog, or crocodile. Instead, they were extremely sophisticated, adapted for moving a large animal fast for long periods of time. You can scare a lizard and it will run very fast for 10 seconds. You can scare a horse, a zebra, or wolf and they can run for 20 minutes to an hour. Big warm-blooded animals tend to have endurance. From their leg construction, you can tell when an animal is made to be an endurance runner. I studied how dinosaur legs were constructed and concluded that they were endurance runners.
   The second evidence comes from my studies on predator-prey relationships. We know that the maximum population of a warm-blooded predator is a 10th or 20th that of a cold-blooded predator in relation to the population size of their prey. This is because cold-blooded animals require much less meat. In Africa, on the average, there is 1 lion per 100 wildebeests, on which lions prey. If you made that lion cold-blooded, it would have 10 or 20 lions per 100 wildebeests. What happens with dinosaur fossil samples? You go out to dig up dinosaurs. Fossils of Allosaurus, a meat-eating dinosaur, are rare, while fossils of Brontosaurus, a plant eater, are very common. Dinosaurian meat eaters are as rare as lions and tigers and saber-toothed cats. That's exactly what they should be if dinosaurs were warm-blooded.
   According to the talk, which of the following were accepted as living dinosaurs by most scholars by 1860?