Assertion:On animal's death , the body stiffens due to hardening of muscle and this is called rigor mortis.
Reason:On animal's death, its muscle soon exhaust ATP and loose the ability to contract or relax.

Options

A. if both assertion and reason are true and the reason is correct explanton of Assertion
B. IF both assertion and reason are true but reason is not a correct explanation of assertion
C. IF assertion is true and reason is wrong
D. if both assertion and reason are wrong

Answer

To analyze the given assertion and reason, we will break down the statements step by step:

### Step 1: Understand the Assertion
- **Assertion**: "On animal's death, the body stiffens due to hardening of muscle and this is called rigor mortis."
- **Explanation**: This statement refers to a physiological phenomenon that occurs after death. Rigor mortis is the postmortem stiffening of the muscles, which occurs due to biochemical changes in the muscle fibers.

**Hint**: Recall what rigor mortis is and its significance in the context of muscle physiology after death.

### Step 2: Understand the Reason
- **Reason**: "On animal's death, its muscle soon exhaust ATP and lose the ability to contract or relax."
- **Explanation**: ATP (adenosine triphosphate) is essential for muscle contraction and relaxation. After death, ATP production ceases, leading to the depletion of ATP in muscle cells. This depletion causes the muscles to become rigid and unable to relax, contributing to the phenomenon of rigor mortis.

**Hint**: Think about the role of ATP in muscle function and what happens to ATP levels after death.

### Step 3: Analyze the Relationship
- The assertion states that rigor mortis is the stiffening of muscles after death, which is true.
- The reason explains that this stiffening occurs because the muscles exhaust ATP and lose the ability to contract or relax, which is also true.
- The reason provides a correct explanation for the assertion.

**Hint**: Consider whether the reason logically supports the assertion and if they are both accurate.

### Step 4: Conclusion
- Both the assertion and reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

**Final Answer**: The correct option is **Option 1**: Both assertion and reason are true, and reason is the correct explanation of assertion.