Which of the following structures represents guanine?

Step-by-step solution

Guanine is a purine nucleobase with the chemical name 2-amino-1H-purin-6(9H)-one. Its structure consists of a fused pyrimidine-imidazole ring system (purine) with a carbonyl group at the C6 position and an amino group at the C2 position. Analyzing the given options: (A) represents Cytosine, which is a pyrimidine derivative with an amino group at C4 and a carbonyl group at C2. (B) represents Guanine, showing the purine ring with a carbonyl at C6 and an amino group at C2. (C) represents Xanthine, a purine derivative