next question: The man flew his airplane over the city and saw pollution visibly in the sky, what was polluted?
Options:
- forest
- street
- air
- caused by humans
- car show
reasoning:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Airplane is flied in the air. The air is polluted which makes the sky look polluted. The answer is air.