In nucleic acid base pairing, which RNA base forms a complementary hydrogen-bonded pair with thymine (T)?

• A. Adenine (A)
• B. Guanine (G)
• C. Cytosine (C)
• D. Uracil (U)

Answer: (A)

Verified step by step guidance

1. Recall that in DNA, the base thymine (T) pairs with adenine (A) through complementary hydrogen bonding.
2. Understand that RNA differs from DNA in that it contains uracil (U) instead of thymine (T).
3. Since thymine is not normally found in RNA, consider which RNA base would pair with thymine if thymine were present.
4. Recognize that adenine (A) pairs with thymine (T) in DNA, so adenine would also form a complementary pair with thymine in RNA.
5. Conclude that the RNA base forming a complementary hydrogen-bonded pair with thymine (T) is adenine (A).