(a) If both assertion and reason are true and the reason is the correct explanation of the assertion of the assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.
Q. Assertion: Amines are basic in nature.
Reason: Presence of lone pair of electrons on nitrogen atom.

Explanation

To solve the question regarding the assertion and reason provided, we need to analyze both statements and determine their validity and relationship.

### Step-by-Step Solution:

1. **Identify the Assertion:**
- The assertion states: "Amines are basic in nature."
- This is true because amines can accept protons (H⁺ ions) due to the presence of a lone pair of electrons on the nitrogen atom.

2. **Identify the Reason:**
- The reason states: "Presence of lone pair of electrons on nitrogen atom."
- This is also true because the lone pair on nitrogen allows it to act as a Lewis base, which is a characteristic of basicity.

3. **Determine the Relationship:**
- Since both the assertion and reason are true, we need to check if the reason correctly explains the assertion.
- The reason does explain why amines are basic: the lone pair on nitrogen can accept protons, making amines basic.

4. **Conclusion:**
- Both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
The correct option is: **(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.**