by adding particle pollution by creating a hole in the ozone layer by causing acid precipitation to fall by increasing the levels of carbon dioxide
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: How has burning fossil fuels most caused a decline to the quality of air that people breathe?
Possibilities:
- by adding particle pollution
- by creating a hole in the ozone layer
- by causing acid precipitation to fall
- by increasing the levels of carbon dioxide

by adding particle pollution