A monopolist is a

Step 1: Analyze the question The question asks for the definition of a monopolist, so we need the option that matches the textbook meaning.

Step 2: Explain the concept "Mono" means one and "poly" means seller. A monopoly is a market structure with these key features:

• One seller or producer controls the whole market supply.
• No close substitutes exist for the product, so buyers cannot easily switch.
• Barriers to entry (such as high capital costs, patents, or government licences) keep other firms out.
• The monopolist is a price maker, so it can control price or output, though not both at once.

Nigerian examples include the former NITEL in telecommunications, and the Nigerian Ports Authority or electricity distribution in certain areas.

Step 3: Evaluate the options

• A. Duopolist: Wrong. A duopoly has two sellers.
• B. Group of producers of related goods: Wrong. This describes an industry or a monopolistically competitive setting, not a single seller.
• C. Partnership business producing a commodity with high demand: Wrong. A monopoly is not defined by the business form (partnership) or by high demand.
• D. Single producer or seller at cheap rate: Wrong. Although it names a single seller, a monopolist typically charges high prices, and low price is not part of the definition.
• E. Single producer or seller of a commodity that has no close substitute: Correct. It captures both essential features: one seller and no close substitutes.

Step 4: Answer

Exam tip: Remember "One seller + No substitute = Monopoly." If an option mentions only one of these, or adds things like "cheap" or "partnership," be suspicious. Also remember: Mono = 1, Duo = 2, Oligo = few.