Assertion : Aniline is better nucleophile than anilium ion.
Reason : Anilium ion have +ve charge.

Options

A. Assertion is correct, reason is correct, reason is a correct explanation for assertion.
B. Assertion is correct, reason is correct, reason is not a correct explanation for assertion
C. Assertion is correct, reason is incorrect
D. Assertion is incorrect, reason is correct.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided:

**Assertion**: Aniline is a better nucleophile than anilinium ion.
**Reason**: Anilinium ion has a positive charge.

### Step-by-Step Solution:

1. **Understanding Aniline and Anilinium Ion**:
- Aniline (C6H5NH2) is an aromatic amine where the amino group (-NH2) is attached to a benzene ring. It has a lone pair of electrons on the nitrogen atom.
- Anilinium ion (C6H5NH3^+) is the protonated form of aniline, where the nitrogen atom has accepted a proton (H^+) and carries a positive charge.

2. **Nucleophilicity**:
- A nucleophile is a species that donates an electron pair to form a chemical bond. The ability of a species to act as a nucleophile is often determined by the availability of lone pairs of electrons.
- In the case of aniline, the nitrogen atom has a lone pair of electrons that can be donated to an electrophile, making it a good nucleophile.

3. **Effect of Charge on Nucleophilicity**:
- The anilinium ion has a positive charge on the nitrogen, which indicates that it has already donated its lone pair of electrons to a proton (H^+). As a result, it lacks a lone pair that can be donated to an electrophile.
- The positive charge also creates an electron deficiency, making it less nucleophilic compared to aniline.

4. **Conclusion**:
- Since aniline has a lone pair of electrons available for donation, it is indeed a better nucleophile than the anilinium ion, which lacks this ability due to the positive charge.
- Therefore, the assertion is true: Aniline is a better nucleophile than anilinium ion.
- The reason is also true: Anilinium ion has a positive charge, which contributes to its reduced nucleophilicity.

### Final Answer:
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct option is **A**.