Purines are adenine and guanine in nucleic acids

Steps:

• Recall that nucleic acid bases divide into purines (double-ring structures) and pyrimidines (single-ring structures).
• Identify purines as adenine (A) and guanine (G).
• Identify pyrimidines as cytosine (C), thymine (T), and uracil (U).
• Match the purine pair to the options provided.

Why C is correct:

• Purines are defined as adenine and guanine, the two larger, double-ringed bases in DNA and RNA.

Why the others are wrong:

• A: Cytosine is a pyrimidine, not a purine.
• B: Both cytosine and thymine are pyrimidines.
• D: Both uracil and cytosine are pyrimidines.

Final answer: C