The correct answer is: A. MR = MC
A pure monopolist is the only seller of a good or service in a market. This means that the monopolist has a great deal of market power and can set the price of its product. The monopolist will choose to produce the level of output where marginal revenue (MR) equals marginal cost (MC). This is because the monopolist will maximize its profits by producing the level of output where the additional revenue from selling one more unit of output is equal to the additional cost of producing that unit of output.
If the monopolist produces at a level of output where MR > MC, then the monopolist is producing too much output. This is because the monopolist is selling units of output where the additional revenue from selling one more unit of output is greater than the additional cost of producing that unit of output. The monopolist could increase its profits by producing less output.
If the monopolist produces at a level of output where MR < MC, then the monopolist is producing too little output. This is because the monopolist is selling units of output where the additional revenue from selling one more unit of output is less than the additional cost of producing that unit of output. The monopolist could increase its profits by producing more output.
Therefore, the equilibrium level of output for the pure monopolist is where MR = MC.