Jim: Kate, look! So many cars on the road. It’s terrible!
Kate: Oh, my god. These cars become snails, and they let out much smoke. Will our city become the second London？
Jim: Yes, it will. People should take some actions to prevent air pollution and make our traffic better.
Kate: Yes, I think so. But what can we do?
Jim: If we can invent a new kind of car, which doesn’t eat any gas but light. Maybe we could alleviate the air pollution made by cars.
Kate: A good idea. But how we make these cars move more quickly? You know, more people buy car now. 
Jim: That’s really a problem. I must think it over. Um, OH! I get it. We can have some cars with wings, just like the flying birds. If so, some cars are moving on the ground, others are flying in the sky, maybe this headachy problem will be solved easily.
Kate: Great. Let’s wish our city traffic a brighter future.