Assertion : `CH_3COOH` and`CH_3COO^-` are acid-base pairs.
Reason : These differ by `H^+`

Options

A. Assertion and reason both are correct statements and Reason is correct explanation for assertion.
B. Assertion and reason both are correct statement but reason is not correct explanation for assertion
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement

Answer

To solve the question regarding the assertion and reason about the acid-base pairs, let's break it down step by step.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- The assertion states that `CH₃COOH` (acetic acid) and `CH₃COO⁻` (acetate ion) are an acid-base pair.

2. **Define Acid and Base**:
- According to the Brønsted-Lowry theory, an acid is a substance that donates a proton (H⁺), while a base is a substance that accepts a proton (H⁺).

3. **Analyze `CH₃COOH`**:
- `CH₃COOH` is acetic acid, which can donate a proton (H⁺) to form `CH₃COO⁻`. Therefore, it acts as an acid.

4. **Analyze `CH₃COO⁻`**:
- `CH₃COO⁻` is the acetate ion, which can accept a proton (H⁺) to revert back to `CH₃COOH`. Therefore, it acts as a base.

5. **Conclusion on Acid-Base Pair**:
- Since `CH₃COOH` donates H⁺ and `CH₃COO⁻` accepts H⁺, they indeed form an acid-base pair.

6. **Difference Between the Two**:
- The difference between `CH₃COOH` and `CH₃COO⁻` is the presence of an H⁺ ion. Thus, they differ by H⁺.

7. **Final Evaluation**:
- Both the assertion and reason are correct. The assertion correctly identifies `CH₃COOH` and `CH₃COO⁻` as an acid-base pair, and the reason correctly explains that they differ by H⁺.

### Final Answer:
Both the assertion and reason are correct.