Which of the following structures represents cytosine?

Step-by-step solution

The given structures represent different nitrogenous bases found in nucleic acids. Structure (A) is Adenine, which is a purine derivative with an amino group at the 6th position. Structure (B) is Guanine, which is a purine derivative with an oxo group at the 6th position and an amino group at the 2nd position. Structure (C) is Thymine, which is a pyrimidine derivative with oxo groups at the 2nd and 4th positions and a methyl group at the 5th position. Structure (D) is Cytosine, which is a pyrimidine derivative with