Concept:A monopolist is a single seller who acts as a price maker in the market.
Explanation:A monopolist has no direct competitor.
Therefore, he can choose the price to charge for his product.
He can also choose the quantity to supply, which then affects the market price.
However, because buyers respond to price, he cannot set both price and quantity freely at the same time.
He must choose either the price he charges or the quantity he supplies, while market demand determines the other.
Answer:D. price or quantity