Which component is found exclusively in DNA?

Thymine is a component that is unique to DNA and is one of the four nitrogenous bases that make up the structure of DNA. In the context of DNA, thymine pairs with adenine through hydrogen bonds, facilitating the double helical structure essential for genetic information storage and replication.

In contrast, uracil is a nitrogenous base that is found exclusively in RNA, where it replaces thymine and pairs with adenine during RNA synthesis. Adenine and guanine, on the other hand, are purines present in both DNA and RNA. This distinction makes thymine the correct choice, as it is not found in RNA and is critical to the structure of DNA.