The correct answer is B. Monopoly.
In a monopoly market, there is only one seller of a good or service. This means that the monopolist has a great deal of market power and can charge a higher price than they would in a more competitive market. The monopolist also has to spend money on advertising and marketing to convince consumers to buy their product, which are known as selling costs.
In a perfect competition market, there are many sellers of a good or service. This means that each seller has very little market power and cannot charge a higher price than the market price. The sellers in a perfectly competitive market also do not have to spend money on advertising and marketing, as consumers are already aware of the products that are available.
In a monopolistic competition market, there are many sellers of a good or service, but each seller offers a slightly different product. This means that each seller has some market power, but not as much as a monopolist. The sellers in a monopolistically competitive market also have to spend money on advertising and marketing to convince consumers to buy their product.
Therefore, the only market structure in which the producer is isolated and selling costs are incurred is a monopoly.