What are nucleotides built from?

Nucleotides are indeed built from three key components: a pentose sugar, a nitrogenous base, and a phosphate group. The pentose sugar can be either ribose or deoxyribose, depending on whether the nucleotide is part of RNA or DNA, respectively. The nitrogenous base can be adenine, guanine, cytosine, thymine (in DNA), or uracil (in RNA). The phosphate group is crucial for linking nucleotides together to form nucleic acids like DNA and RNA, allowing for the formation of the backbone of these molecules.

The other options mention components that do not accurately represent the structure of nucleotides. For instance, a hexose sugar and a hydroxyl group do not fit the definition of a nucleotide's basic structure. Similarly, amino acids and fatty acids are not parts of nucleotides, further clarifying why only the first option correctly describes the components of nucleotides.