Assertion: `C_(p)` can be less than `C_(V)`.
Reason: `C_(p)C_(V)=R` is valid only for ideal gases.

Options

A. If both assertion and Reason are true and the Reason is the correct explanation of the assertion.
B. If both assertion and Reason are true but the reason is not the correct explanation of the assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understanding the Assertion
The assertion states that \( C_p \) (specific heat at constant pressure) can be less than \( C_v \) (specific heat at constant volume).

### Step 2: Understanding Specific Heats
- **Specific Heat at Constant Volume (\( C_v \))**: When heat is added to a substance at constant volume, all the heat goes into changing the internal energy of the substance, as there is no work done (since volume does not change).
- **Specific Heat at Constant Pressure (\( C_p \))**: When heat is added at constant pressure, some of the heat goes into doing work (expanding the substance), and the rest goes into changing the internal energy.

### Step 3: Analyzing the Relationship
In general, for most substances, \( C_p \) is greater than \( C_v \) because at constant pressure, some energy is used for work done against the external pressure. However, the assertion claims that \( C_p \) can be less than \( C_v \). This can happen in certain non-ideal conditions or specific materials under certain circumstances.

### Step 4: Understanding the Reason
The reason states that the equation \( C_p C_v = R \) is valid only for ideal gases. However, the correct relationship for ideal gases is actually \( C_p - C_v = R \). This means that the reason given does not correctly explain the assertion.

### Step 5: Conclusion
Both the assertion and the reason are true statements:
- **Assertion**: \( C_p \) can be less than \( C_v \) (true under specific conditions).
- **Reason**: The relationship \( C_p - C_v = R \) is valid only for ideal gases (true, but does not explain the assertion).

Thus, the correct answer is that both statements are true, but the reason does not correctly explain the assertion.

### Final Answer
- **Assertion**: True
- **Reason**: True, but does not explain the assertion.