In the following acid-base reaction, in which can backward reaction if favoured?

Options

A.
B. `KH + EtOH iff `
C.
D.

Explanation

To determine in which acid-base reaction the backward reaction is favored, we need to analyze the nature of the acids and bases involved in each option. The backward reaction is favored when we have a weak acid and a weak base.

### Step-by-Step Solution:

1. **Understand the Concept of Acid-Base Reactions**:
- An acid-base reaction involves the transfer of a proton (H⁺) from the acid to the base.
- The forward reaction occurs when the acid donates a proton, while the backward reaction occurs when the base donates a proton back to the acid.

2. **Identify the Nature of Acids and Bases in Each Option**:
- Weak acids and weak bases can favor the backward reaction, while strong acids and strong bases tend to favor the forward reaction.

3. **Analyze Each Option**:
- **Option 1: E p O⁻ + H⁺**
- E p O⁻ is a conjugate base and is stabilized by resonance. The reaction proceeds forward, favoring the formation of products.
- **Option 2: K⁺ + E p O⁻ + H⁺**
- E p O⁻ reacts with H⁺ to form K⁺ and H₂. This reaction also proceeds forward, thus not favoring the backward reaction.
- **Option 3: Me₃C⁻ + H₂O**
- Me₃C⁻ is a strong base and accepts a proton from water, leading to a forward reaction. This option does not favor the backward reaction.
- **Option 4: O⁻ + CH₃OH**
- O⁻ is a weak base and does not readily accept a proton due to resonance stabilization. When CH₃OH loses a proton, it forms CH₃O⁻, which can easily revert back to CH₃OH. This indicates that the backward reaction is favored.

4. **Conclusion**:
- The reaction in **Option 4 (O⁻ + CH₃OH)** is the one where the backward reaction is favored due to the presence of a weak base (O⁻) and a weak acid (CH₃OH).

### Final Answer:
The backward reaction is favored in **Option 4: O⁻ + CH₃OH**.