voluntary exchange\na. relates to price ceilings and price floors.\nb. is not part of the market system.\nc…

Brief Explanations:

Voluntary exchange in a market - based system occurs when both parties believe they will gain from the trade. Price - ceilings and floors are government - imposed restrictions and not directly related to voluntary exchange. Voluntary exchange is a fundamental part of the market system. It is a mutually beneficial activity where both parties are better off.

Answer:

D. makes both parties to a trade better off.