Assertion:Extensor muscles of the back in man are red muscles.
Reason:They are undergo slow sustained contraction for long periods.

Options

A. if both assertion and reason are true and the reason is correct explanton of Assertion
B. IF both assertion and reason 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 solve the question regarding the assertion and reason about the extensor muscles of the back in humans, let's break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "Extensor muscles of the back in man are red muscles."
- Red muscles, also known as slow-twitch muscles, are characterized by a high concentration of myoglobin and mitochondria. This allows them to sustain prolonged activity and resist fatigue.

### Step 2: Evaluate the Reason
The reason provided is "They undergo slow sustained contraction for long periods."
- This statement is true as well. Red muscles are designed for endurance and can contract slowly and sustain activity over extended periods without tiring quickly.

### Step 3: Analyze the Relationship
Now we need to determine if the reason correctly explains the assertion.
- Since red muscles (extensor muscles) indeed undergo slow sustained contractions, the reason supports the assertion.

### Step 4: Conclusion
Both the assertion and reason are true, and the reason is the correct explanation of the assertion. Therefore, the correct answer is:
- **Option 1: Both assertion and reason are true, and reason is the correct explanation of assertion.**