Assertion : Cardiac muscles contract rapidly like striated muscles but do not undergo fatigue.
Reason : Cardiac muscles contract rhythmically.

Options

A. If both Assertion and Reason are true but Reason is not a correct explanation of Assertion
B. If both Assertion and Reason are true but Reason is not a correct explanation of Assertion.
C. If Assertion is true but Reason is False
D. If both Assertion and Reason are false

Answer

To solve the question regarding the assertion and reason related to cardiac muscles, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Cardiac muscles contract rapidly like striated muscles but do not undergo fatigue."
- Cardiac muscles are indeed striated (they have a banded appearance) and contract quickly. However, unlike skeletal muscles, they do not experience fatigue due to their unique structure and energy supply.

2. **Understanding the Reason**:
- The reason states that "Cardiac muscles contract rhythmically."
- This is true; cardiac muscles have a natural rhythm and are responsible for the heartbeat, which is controlled by the sinoatrial node in the heart.

3. **Evaluating the Relationship**:
- The assertion is true because cardiac muscles do contract rapidly and do not fatigue.
- The reason is also true because cardiac muscles contract rhythmically.
- However, the reason does not directly explain the assertion. The fact that cardiac muscles contract rhythmically does not inherently explain why they do not undergo fatigue.

4. **Conclusion**:
- Both the assertion and the reason are true, but the reason does not adequately support the assertion. Therefore, the correct conclusion is that both the assertion and the reason are true, but the reason is not the correct explanation for the assertion.

### Final Answer:
- Both assertion and reason are true, but the reason is not the correct explanation for the assertion.