Amonopoly is a market that has
a) few competing businesses.
b) many sellers of the same item.
c) many sellers of a variety of products.
d) a single supplier of a good or service.

The correct answer is: Option D. A single supplier of a good or service.

A monopoly is defined as the possession or absolute control over a supply or trade in a commodity or service.

With the lack of restraints or regulations in a market, one single corporation is capable of dominating a sector or industry, and therefore, become the "single supplier of a good or service" with no pressure from potential competitors.