A : Glycine is the only amino acid which is optically inactive.
R : Glycine has no chiral carbon.

Options

A. If both Assertion and Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion and Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that glycine is the only amino acid that is optically inactive. To evaluate this, we need to understand what optical inactivity means. An optically inactive compound does not rotate plane-polarized light, which is typically due to the absence of chiral centers.

2. **Identifying Glycine's Structure**: Glycine is the simplest amino acid with the chemical structure NH2-CH2-COOH. In this structure:
- NH2 is the amino group.
- CH2 is the carbon backbone.
- COOH is the carboxyl group.

3. **Determining Chirality**: A chiral carbon is a carbon atom that is bonded to four different groups. In glycine, the central carbon (the one bonded to the amino group, carboxyl group, and the hydrogen) is attached to two hydrogen atoms and one carboxyl group, making it impossible for it to have four different substituents.

4. **Conclusion on Assertion**: Since glycine has no chiral carbon, it cannot be optically active. Therefore, the assertion is true.

5. **Understanding the Reason**: The reason states that glycine has no chiral carbon. This is indeed true, as explained in the previous step.

6. **Evaluating the Relationship**: The reason correctly explains why the assertion is true. Since glycine lacks a chiral carbon, it is indeed optically inactive.

### Final Answer:
Both the assertion (A) and the reason (R) are true, and R is the correct explanation of A.

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