Step 1: Understand that market structures in microeconomics describe the organization and characteristics of different markets based on the number of firms, product differentiation, and barriers to entry.
Step 2: Identify the four basic market structures commonly studied: Perfect competition, Monopolistic competition, Oligopoly, and Monopoly.
Step 3: Recognize that 'duopoly' and 'monopsony' are specific cases or concepts related to market structures but are not part of the four basic categories. A duopoly is a special case of an oligopoly with only two firms, and a monopsony refers to a market with a single buyer.
Step 4: Review the options given and match them against the four basic market structures: Perfect competition, Monopolistic competition, Oligopoly, and Monopoly.
Step 5: Conclude that the correct set of four basic market structures is: Perfect competition, Monopolistic competition, Oligopoly, and Monopoly.