Acartel differs from a monopoly in that
a. one firm sets the prices for all goods in an industry.
b. one corporation has complete control of a product or service.
c. all the firms involved in the same business merge into one entity.
d. businesses making the same product agree to limit production.

A cartel differs from a monopoly in that with a cartel you have multiple businesses making the same product which then agree on limiting production. Through this they manipulate the price then. This is not something a monopoly does, a monopoly is usually one company which has all the maret share over certain goods.