Which of the following is a major pyrimidine found in DNA?

Cytosine is a major pyrimidine found in DNA. In the structure of DNA, pyrimidines consist of single-ring structures, and cytosine is one of the two types of pyrimidines that pair with purines during the formation of nucleotide sequences. The other pyrimidine in DNA is thymine, which is not listed as an option.

In contrast, adenine and guanine are purines, characterized by their double-ring structures, and are not classified as pyrimidines. Uracil is a pyrimidine as well, but it is primarily found in RNA and not in DNA. Thus, among the options provided, cytosine is the correct and relevant choice related to its presence in DNA. Understanding the types of nucleotides and their structures is fundamental in biochemistry, particularly in the context of nucleic acid composition and function.