Choose from:
I. mammals
II. clouds
III. humans
IV. penguins
V. jellyfish
VI. warm-blooded
VII. fur and fat
VIII. animals

You are presented with the quiz "what are endothermic tetrapod vertebrates?" 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 "penguins are a type of birds". So, what's the best answer to the question?
Answer:
IV.