Assertion :- Antiparallel polarity helps in stability of DNA.
Reason : It allows complementary pairing between base pairs.

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that "Antiparallel polarity helps in stability of DNA."
- Antiparallel polarity refers to the orientation of the two strands of DNA, where one strand runs in a 5' to 3' direction and the other runs in a 3' to 5' direction. This orientation is crucial for the structure and function of DNA.

2. **Understanding the Reason:**
- The reason given is "It allows complementary pairing between base pairs."
- Complementary pairing refers to the specific pairing of nitrogenous bases in DNA: adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). This pairing is facilitated by hydrogen bonds.

3. **Analyzing the Relationship:**
- The assertion is true because the antiparallel arrangement of DNA strands indeed contributes to the stability of the DNA molecule. This stability is due to the proper alignment of base pairs, which allows for effective hydrogen bonding.
- The reason is also true because the antiparallel nature of the strands allows for the correct complementary base pairing, which is essential for the integrity of the DNA structure.

4. **Conclusion:**
- Both the assertion and the 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 for the assertion.

### Final Answer:
**Option A:** Both assertion and reason are true, and reason is the correct explanation for assertion.

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