Answer:
The correct option here is C) larger barriers to entry.
Step-by-step explanation:
A monopoly is a form of market where the number of sellers won't be much, as much of the market share is with one company, a really good example of it is Microsoft owning windows operating system.
Here the firms are price makers not price takers , as in monopoly a firm can control both supply and price of goods and service, as if a firm decides to decrease the supply it can sell products at a high cost.
It is really difficult for a new firm to enter in to market if the monopoly has been established , since there would be large initial cost to be incurred for entering and also it will be difficult for the new firm top compete with old one in taking over market share, so that it can also achieve similar low costs as of old one ( monopolist one )