One defining characteristic of pure monopoly is that: the monopolist is a price taker. the monopolist uses advertising. the monopolist produces a product with no close substitutes. there is relatively easy entry into the industry, but exit is difficult.

One defining characteristic of pure monopoly is that the monopolist produces a product with no close substitutes. A pure monopoly is a market structure where there is a single company that produces a product and there is not another company that produces a product remotely similar. Due to not having another substitute the company with the product that is the only one available becomes a pure monopoly. 

The answer is a. i think