a bus a helicopter a rocket a train
I gave my students this multiple choice question: A squid is an animal that lives in the ocean. It pumps a stream of water out of its body, causing it to move rapidly. Which of the following mechanical systems moves in a way most similar to the squid?

Only one answer is correct among these 4 choices:
- a bus
- a helicopter
- a rocket
- a train

Could you tell me which one is correct?

a rocket