Which of the following does not represent a redox reaction ?

Options

A. `H_2S + Cl_2 to S + 2HCl `
B. `CuO + H_2 to Cu + H_2O`
C. `ZnO + C overset("heat")toZn + CO`
D. `2NaOH + H_2SO_4 to Na_2SO_4 + 2H_2O`

Explanation

To determine which of the following does not represent a redox reaction, we first need to understand what a redox reaction is. A redox (reduction-oxidation) reaction involves the transfer of electrons between two species, resulting in changes in their oxidation states. Oxidation refers to the loss of electrons (or the addition of oxygen), while reduction refers to the gain of electrons (or the removal of oxygen).

### Step-by-Step Solution:

1. **Identify the Reactions**: We need to analyze the given options (A, B, C, D) to see if they involve oxidation and reduction processes.

2. **Understand Redox Reactions**: Recall that in a redox reaction:
- Oxidation involves the loss of electrons or the addition of oxygen.
- Reduction involves the gain of electrons or the removal of oxygen.

3. **Analyze Each Option**:
- **Option A**: If this option involves a reaction where there is a transfer of electrons (oxidation and reduction), it is a redox reaction.
- **Option B**: Similarly, if this option shows a change in oxidation states due to electron transfer, it is a redox reaction.
- **Option C**: Check if there is an addition of oxygen or removal of hydrogen, indicating oxidation or reduction.
- **Option D**: If this option describes a neutralization reaction (acid + base → salt + water), it does not involve electron transfer and thus does not represent a redox reaction.

4. **Conclusion**: After analyzing all options, we find that **Option D** represents a neutralization reaction and does not involve oxidation or reduction. Therefore, it is the correct answer to the question.

### Final Answer:
**Option D does not represent a redox reaction.**