The correct answer is: "market power".
The mentioned firm controls the whole market share, hence, it operates as a monopoly. It has market power, therefore, the monopoly can fix a price for its products or services which is higher than the one that would result in a perfectly competitive market.
Still, the monopolist faces a negative demand curve. If the price fixed is too high, consumers can decide not to consume it at all, either because they do not assign such a large value to the product to pay so much for it, or because they cannot afford it. So the market power is not absolute, but large if compared to the conditions in which firms usually operate in other market structures.