Pricing and Output decisions of sellers are highly inter-dependent in markets known as _________

Step 1: Analyze the question The question asks which market structure has sellers whose pricing and output decisions are highly inter-dependent. This means that what one firm does directly affects the others, and each firm must anticipate how its rivals will react.

Step 2: Explain the concept Interdependence depends on the number of sellers and how much market power each one holds:

• Monopoly: There is only one seller, so there are no rivals to depend on.
• Oligopoly: A few large firms dominate the market. Each firm's price or output change noticeably affects the others, so they watch each other closely. Examples in Nigeria are the telecom industry (MTN, Airtel, Glo, 9mobile), cement (Dangote, BUA, Lafarge), and the banking sector.
• Monopolistic competition: There are many firms selling differentiated products, such as restaurants or hair salons. Each firm acts mostly on its own because it is small relative to the market.
• Perfect competition: There are very many sellers of identical products, and each is a price taker. No single firm can influence the others.

Step 3: Solution Because the market has only a few big sellers, a price cut by one (for example, MTN reducing data prices) forces the others to respond, or they lose customers. This mutual dependence is the defining feature of an oligopoly. It is also why oligopolists often engage in collusion or form cartels (like OPEC), and why the kinked demand curve model is used to explain their price rigidity.

Step 4: Answer The correct option is B. Oligopoly.

Tip: Remember "Oli-gopoly = Few, Follow": a few firms, and they follow each other's moves. When you see the words inter-dependent, few sellers, cartel, or kinked demand curve in a JAMB question, think oligopoly.