Concept:A monomer is the small repeating unit that joins together to form a polymer. Natural rubber is a polymer made from a single type of monomer.Explanation:Natural rubber is chemically called polyisoprene. Its monomer is isoprene, which has the IUPAC name 2‑methylbut‑1,3‑diene. The other options are synthetic polymers: Neoprene (synthetic rubber from chloroprene), Terylene (polyester from ethylene glycol and terephthalic acid), and Orlon (polyacrylonitrile from acrylonitrile). Only isoprene forms natural rubber.Answer:B. Isoprene