Identify a side chain (R) group present in serine, an amino acid.

Step-by-step solution

An amino acid has the general structure H ₂ N – CHR – COOH , where R represents the side chain. For serine, the side chain is the hydroxymethyl group, – CH ₂ OH . Analyzing the options: A) CH ₃– corresponds to alanine B) H ₃ C – CHOH – corresponds to threonine C) Me ₂ CH – (equivalent to – CH ( CH ₃)₂ ) corresponds to valine D) HO – CH ₂– (equivalent to – CH ₂ OH ) matches serine The correct representation of serine's R group is therefore option D.