Assertion (A): In dilute benzene solutions, equimolar addition of `R_(3)N` and `HCI` produce a substance with a dipole moment. In the same solvent, equimolar addition of `R_(3)N` and `SO_(3)` produce a substance having an almost identical dipole moment.
Reason (R) : Both `HCI` and `SO_(3)` are Lewis acids and can react with the amine base to form polar substances which undergo ionic dissociation in a solvent sufficiently more polar than benzene.
Moreover, `(N-S)` bond is a more polar bond.

Options

A. If both (A) and (R) are correc, and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect, but (R) is correct.

Explanation

To solve the given question, we need to analyze the assertion and reason provided, and determine their validity based on the principles of ionic equilibrium and Lewis acid-base theory.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that in dilute benzene solutions, equimolar addition of a tertiary amine (R₃N) and HCl produces a substance with a dipole moment. Similarly, the addition of R₃N and SO₃ also produces a substance with an almost identical dipole moment.
- **Analysis**: Tertiary amines can act as Lewis bases due to the presence of a lone pair of electrons on the nitrogen atom. HCl, being a strong acid, can react with the amine to form an ionic compound, which is polar due to the presence of the N-H bond. SO₃ can also act similarly, forming a polar compound with the amine.

2. **Understanding the Reason (R)**:
- The reason states that both HCl and SO₃ are Lewis acids and can react with the amine base to form polar substances, which undergo ionic dissociation in a solvent that is more polar than benzene. It also mentions that the N-S bond is a more polar bond.
- **Analysis**: HCl is indeed a Lewis acid because it can accept a pair of electrons from the amine. SO₃ also acts as a Lewis acid due to its ability to accept electron pairs. The formation of polar substances is consistent with the behavior of these acids reacting with the amine. The N-S bond being more polar than the N-Cl bond further supports the assertion.

3. **Conclusion**:
- Both the assertion and the reason are correct. The reason provides a valid explanation for the assertion. Therefore, the correct answer is that both the assertion and reason are true, and the reason correctly explains the assertion.

### Final Answer:
Both Assertion (A) and Reason (R) are correct, and R is the correct explanation of A.