The Chinese alligator is a kind of crocodile unique to China, mainly distributed in the middle and lower reaches of the Yangtze River. It is an ancient and very rare reptile. An existing crocodile can also find many characteristics of dinosaurs, often called "Living fossils". Therefore, the Chinese alligator is of great significance for people to study the rise and decline of ancient reptiles, and to study the evolution of paleogeology and organisms. Which of the following, if true, is the prerequisite for the above argument? ['lligator is one of the rarest reptiles in the world.', 'he age of the B alligator was about the same as that of the dinosaur.', 'ew existing animals with dinosaur-like reptile characteristics.', 'tudying the characteristics of dinosaur reptiles is the key to studying the rise and fall of ancient reptiles.']