- Coal is a kind of fossil fuel
- Oil is a kind of fossil fuel
- Burning fossil fuels releases sulfur dioxide into the atmosphere
- So, burning coal and oil releases sulfur dioxide into the atmosphere

- Burning coal and oil releases sulfur dioxide into the atmosphere
- Sulfur dioxide is a kind of gas
- Sulfur dioxide dissolving in water causes acid rain
- Therefore, gases from burning coal and oil dissolving in water in the atmosphere causes acid rain

Hence, gases from burning coal and oil dissolving in water in the atmosphere causes acid rain
Question: One of the principal causes of acid rain is
Context: - Coal is a kind of fossil fuel 
- Oil is a kind of fossil fuel 
- Sulfur dioxide is a kind of gas 
- Burning fossil fuels releases sulfur dioxide into the atmosphere 
- Sulfur dioxide dissolving in water causes acid rain