Final answer:
The monomer used for enzyme synthesis is an amino acid, as enzymes are a type of protein which are composed of chains of amino acids arranged in specific sequences coded by DNA.
Step-by-step explanation:
The monomer used for the synthesis of an enzyme is B) Amino acid. Enzymes are a type of protein, and proteins are made up of long chains of amino acids. The sequence of amino acids determines the enzyme's unique shape and function. The DNA sequence contains the instructions to arrange these amino acids into a specific order during protein synthesis.
Each of the other options listed - nucleotide, fatty acid, and monosaccharide - are monomers for other types of biological molecules. Nucleotides are the monomers of nucleic acids such as DNA and RNA, fatty acids are components of lipids, and monosaccharides are the monomers of carbohydrates.