It's not A or B because neither have any effect on air pollution. Air conditioners or heaters just change the temperature of the air by filling the room in. Products being reused or disposed makes no difference on air, although it can make a big impact on whether the environment stays green so to speak.
The answer is C.
Hazardous waste are different. They are dangerous, suffocating, and irritating. They are pretty much chemicals that people should be careful of using. It's even worse if it's not disposed of properly. The name hazardous itself explains the danger. It is something that can pollute the environment if not taken care of properly.
