You are presented with the quiz "Which animals have a circulatory system?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "mollusks have a circulatory system with one or two hearts that pump blood" and "interestingly, a squid is also a mollusk". So, what's the best answer to the question?
Select from: 1. insects 2. mammals 3. fur seals 4. sharks 5. cows 6. squids 7. a fish 8. chickens
Answer:
6.