Final answer:
The variable structures of a nucleotide include the sugar, the base, and the phosphate group. These components are fundamental to the nucleotide's structure, which forms the building blocks of DNA and RNA.
Step-by-step explanation:
The variable structures of a nucleotide include the sugar, the base, and the phosphate group. A nucleotide consists of these three fundamental components, which combine to form the building blocks of nucleic acids such as DNA and RNA. The sugar can be either deoxyribose in DNA or ribose in RNA. The nitrogenous base attached to the sugar can vary among adenine, guanine, cytosine, thymine (in DNA), or uracil (in RNA). Lastly, the phosphate group(s) can be present in one to three numbers, leading to the formation of nucleoside monophosphate, diphosphate, or triphosphate structures.
A nucleotide is made up of three components: a phosphate group, a pentose sugar, and a nitrogen-containing base. The variable structures of a nucleotide include the base, the sugar, and the phosphate group. The base is the nitrogen-containing component of the nucleotide, while the sugar is the pentose sugar (deoxyribose in DNA and ribose in RNA) and the phosphate group is the group that contains phosphorus and oxygen atoms. Therefore, option (c) is the correct answer, as it includes both the sugar and the base as the variable structures of a nucleotide.