Why is addition polymerization also known as vinyl polymerization?

• A. monomers are unsaturated compounds
• B. its a chain reaction
• C. most monomers contain (CH₂‚Äö√Ñ√∂‚àö√ò‚àö‚Ñ¢CH‚Äö√Ñ√∂‚àö√Ü‚àö√ë) group
• D. all of the mentioned