Assertion (A): Mendel chose a number of varieties of garden pea as plant material for his experiments.
Reason (R): Garden pea has well defined characters and is bisexual.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is NOT the correct explanation of A.
C. A is true but R is false.
D. A is false and R is true.

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**: The assertion states that Mendel chose a number of varieties of garden pea as plant material for his experiments. This is a factual statement based on Mendel's historical experiments in genetics.

2. **Understanding the Reason (R)**: The reason provided states that garden pea has well-defined characters and is bisexual. This is also true, as garden peas exhibit distinct traits (like flower color, seed shape, etc.) that can be easily observed and measured. Additionally, being bisexual means that the plants have both male and female reproductive organs, allowing for self-fertilization and controlled cross-fertilization.

3. **Evaluating the Relationship**: Now, we need to determine if the reason explains the assertion. Mendel's choice of garden pea was indeed influenced by its well-defined characters and its bisexual nature. These characteristics made it easier for him to conduct experiments on inheritance patterns.

4. **Conclusion**: Since both the assertion and the reason are correct, and the reason accurately explains why Mendel chose garden pea for his experiments, we can conclude that the correct option is:
- **Option 1**: Both are correct. Assertion is correct and reason is explaining the assertion.