Assertion : The heart of fish contains only deoxygenated blood.
Reasoning : Oxygenated blood does not return back to the heart in fishes.

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.

Answer

To solve the assertion and reasoning question, we will evaluate both the assertion and the reasoning separately before concluding whether they are true or false.

### Step-by-Step Solution:

**Step 1: Analyze the Assertion**
- The assertion states that "The heart of fish contains only deoxygenated blood."
- Fish have a two-chambered heart, consisting of one atrium (auricle) and one ventricle.
- In fish, the heart pumps deoxygenated blood to the gills, where it gets oxygenated.
- Therefore, the assertion is **true**.

**Step 2: Analyze the Reasoning**
- The reasoning states that "Oxygenated blood does not return back to the heart in fishes."
- After the gills oxygenate the blood, this oxygen-rich blood is distributed to the body.
- The deoxygenated blood from the body returns to the heart, but the oxygenated blood does not return to the heart.
- Thus, the reasoning is also **true**.

**Step 3: Determine the Relationship Between Assertion and Reasoning**
- The reasoning provides an explanation for the assertion. It clarifies why the heart of fish contains only deoxygenated blood: because the oxygenated blood does not return to the heart.
- Therefore, both the assertion and the reasoning are true, and the reasoning correctly explains the assertion.

### Conclusion:
The correct answer is that both the assertion and the reasoning are true, and the reasoning is the correct explanation for the assertion.

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