What is a nucleotide composed of?

A nucleotide is indeed composed of three main components: a sugar, a phosphate group, and a nitrogenous base. In the context of DNA, the sugar is deoxyribose, while in RNA, it is ribose. Each nucleotide includes one of the four nitrogenous bases (adenine, thymine, guanine, and cytosine for DNA; adenine, uracil, guanine, and cytosine for RNA). Together, these components form the basic building blocks of nucleic acids.

The mention of "a deoxyribose, a phosphate, and a base pair" correctly highlights that the sugar (deoxyribose) and phosphate group are crucial parts of a nucleotide, along with the implication of a nitrogenous base, although the term "base pair" refers more to the pairing of two bases in the context of DNA structure rather than part of a single nucleotide. Thus, this choice encapsulates the essential structural components of nucleotides necessary for forming the larger structures of DNA and RNA.