Step 1: Identifying what makes rain acidic.
Pure rainwater is slightly acidic due to dissolved carbon dioxide, but acid rain is much more acidic than normal rain.
This high acidity must come from strong acids formed in the atmosphere.
Step 2: Tracing the source of strong acids.
Strong acids like sulfuric acid and nitric acid are not released directly into the air.
Instead, they are produced when certain gaseous pollutants react with oxygen and water vapor.
Step 3: Key atmospheric reactions.
Sulphur dioxide undergoes oxidation to form sulfuric acid:
\[ \text{SO}_2 \rightarrow \text{H}_2\text{SO}_4 \]
Nitrogen dioxide reacts similarly to form nitric acid:
\[ \text{NO}_2 \rightarrow \text{HNO}_3 \]
These reactions occur in clouds and moist air, leading to acidic precipitation.
Step 4: Eliminating non-responsible gases.
CO and CO\(_2\) do not produce strong acids responsible for acid rain.
O\(_3\) and PAN are linked to photochemical smog.
NH\(_3\) can neutralize acids, and CH\(_4\) mainly contributes to global warming.
Final Conclusion:
The gases mainly responsible for the formation of acid rain are:
\[ \boxed{\text{NO}_2 \text{ and SO}_2} \]