Assertion (A): Aminoacylation is an essential step for the synthesis of protein.
Reason (R): It is the process of adding an activated amino acid to the acceptor arm of a transfer RNA.

Options

A. Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A)
B. Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
C. Assertion (A) is true but reason (R) is false.
D. Assertion (A) is false but reason (R) is true.

Explanation

### Step-by-Step Solution

1. **Understanding the Assertion**: The assertion states that "Aminoacylation is an essential step for the synthesis of protein." To evaluate this, we need to understand what aminoacylation is and its role in protein synthesis.

2. **Defining Aminoacylation**: Aminoacylation refers to the process of attaching an amino acid to its corresponding transfer RNA (tRNA). This is a crucial step in the translation phase of protein synthesis, as it ensures that the correct amino acid is added to the growing polypeptide chain.

3. **Understanding the Reason**: The reason provided states, "It is the process of adding an activated amino acid to the acceptor arm of a transfer RNA." This accurately describes the process of aminoacylation, where an amino acid is linked to the tRNA molecule at its acceptor arm.

4. **Linking Assertion and Reason**: Since aminoacylation is indeed essential for protein synthesis (as it provides the necessary amino acids for building proteins), and the reason correctly describes how this process occurs, we can conclude that both the assertion and the reason are true.

5. **Conclusion**: Both the assertion (A) and the reason (R) are true, and the reason provides a correct explanation for the assertion. Therefore, the answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.