What is being asked?

We need the correct and complete reaction that represents acid rain caused by $SO_2$.

Acid rain due to sulphur dioxide ultimately means formation of sulphuric acid, $H_2SO_4$, in the atmosphere.

How does $SO_2$ cause acid rain?

The overall process is:

• $SO_2$ gets oxidized to $SO_3$
• $SO_3$ reacts with water to form $H_2SO_4$

Combining these steps gives the net reaction: $2SO_2 + O_2 + 2H_2O \to 2H_2SO_4$

Check each option

Option A: $2SO_2 + O_2 \to 2SO_3$ This is only the oxidation step. It does not show acid formation. So it is incomplete.

Option B: $SO_2 + O_3 \to SO_3 + O_2$ This also only shows oxidation of $SO_2$ to $SO_3$. Again, no acid is formed, so it is incomplete.

Option C: $SO_2 + H_2O_2 \to H_2SO_4$ This reaction can occur in atmospheric chemistry, but the question asks for the correct and complete reaction to represent acid rain caused by $SO_2$ in the usual overall sense. The standard complete net reaction is the one involving oxygen and water explicitly.

Option D: $2SO_2 + O_2 + 2H_2O \to 2H_2SO_4$ This shows:

• oxidation of $SO_2$
• presence of water
• direct formation of sulphuric acid

Hence this is the correct and complete representation.

Final answer

The correct option is: $\boxed{D}$

Comparison with stored answer

Stored correct answer: $D$

My derived answer matches the stored answer.