Step 1: Understanding the Concept
Thermocol is expanded polystyrene, a foam made by blowing gas into polystyrene beads.
Step 2: Monomer
Polystyrene is an addition polymer formed by polymerisation of styrene (vinylbenzene).
Step 3: Compare the options
Bisphenol is used for polycarbonates and epoxy resins, vinyl chloride gives PVC and butadiene gives synthetic rubber.
Final Answer:
Thermocol is obtained from styrene.
\[ \boxed{\text{(C) }\text{Styrene}} \]