I think the answer is evolution.
Answer: Air pollution is responsible for seven million deaths each year in the US
Explanation: https://www.who.int/health-topics/air-pollution#:~:text=The%20combined%20effects%20of%20ambient,cancer%20and%20acute%20respiratory%20infections.
The leafs would contain more Chloroplasts, that is where photosynthesis occurs!
The reactivity of an atom is due to the number and arrangement of Electrons (b) in the outer energy level.
Electrons "bond" they're the ones that react to create other elements.
Examples: Salt (NaCl) Carbon Dioxide (CO2)
And so on, and so forth. Thus, your answer....B.