Answer:
Monopoly->There is a single seller in the market
Oligopoly->Every company in this market structure is aware of the actions of other companies.
Perfect Competition->There are no barriers to entry in the market.
Collusion->Three companies secretly enter into a price agreement.
Step-by-step explanation:
monopoly—a situation in which a single seller (or group of sellers) is the only producer or supplier of a product in a market, preventing any form of competition in the market
oligopoly—a market structure dominated by a few companies
perfect competition—a market structure in which there are many sellers and buyers of homogeneous products
collusion—a secret agreement to set production and price limits