waste acid from chemical factories being pumped into rivers acid from chemical laboratories evaporating into the air gases from burning coal and oil dissolving in water in the atmosphere gases from air conditioners and refrigerators escaping into the atmosphere
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: One of the principal causes of acid rain is
Possibilities:
- waste acid from chemical factories being pumped into rivers
- acid from chemical laboratories evaporating into the air
- gases from burning coal and oil dissolving in water in the atmosphere
- gases from air conditioners and refrigerators escaping into the atmosphere

gases from burning coal and oil dissolving in water in the atmosphere