Assertion (A): The enthalpy of both graphite and diamond is taken to be zero, being elementary substances
Reason (R ) : The enthalpy of formation of an elementary substance in any state is taken as zero.

Options

A. If both (A) and (R ) are correct, and (R ) is the correct explanation for (A).
B. If the both (A) and (R ) are correct, but(R ) is not a correct explanation for (A).
C. If (A) is correct, but (R ) is incorrect.
D. If both (A) and (R ) are incorrect.

Explanation

To analyze the assertion and reason provided in the question, let's break down the statements step by step.

### Step 1: Understand the Assertion
The assertion states: "The enthalpy of both graphite and diamond is taken to be zero, being elementary substances."

- **Analysis**:
- Graphite is indeed a form of carbon and is considered the standard state of carbon at room temperature and pressure (298 K and 1 atm).
- However, diamond, while also a form of carbon, is not the standard state of carbon. Therefore, the enthalpy of diamond cannot be considered zero in the same way as graphite.
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