Q: You are presented with the quiz "What kind of animal would be an endothermic tetrapod vertebrate?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "birds are endothermic tetrapod vertebrates" and "class Aves is for the birds, literally". So, what's the best answer to the question?

Choose from: 1). animals in the class aves; 2). barks and snarls; 3). passenger pigeons; 4). Something that is self-aware; 5). Generating heat; 6). retaining heat; 7). absorb light energy; 8). it keeps an organism warm;
The answer is:
1).