Uracil's structure and base pairing in RNA

Steps:

• Identify uracil as a pyrimidine nucleotide base found in RNA, with a single six-membered ring.
• Confirm pyrimidines like uracil have one ring, unlike purines (adenine, guanine) with fused rings.
• Recall uracil base-pairs with adenine using two hydrogen bonds.
• Select the option matching true for single ring (✓), false for purine (×), and true for two hydrogen bonds (✓).

Why A is correct:

• It accurately reflects uracil's pyrimidine nature (single ring, not purine) and pairing rule with adenine via two hydrogen bonds, per nucleic acid base-pairing laws.

Why the others are wrong:

• B incorrectly claims single ring false, purine true, and two bonds false.
• C incorrectly claims single ring false and purine false but repeats two bonds true without full accuracy.
• D incorrectly claims single ring false and purine false, mismatching uracil's structure.

Final answer: A