Answer: C) Marginal cost may change but marginal revenue remains the same
Step-by-step explanation:
In a perfect competition the price is set by the market which means that one individual firm cannot change the price. This means that the marginal revenue for everyone is the same. If your firm decided to double its output, total revenue might change but marginal revenue will remain the same.
The marginal cost may change as well because marginal cost is unique to firms so if your firm wants to double output, it might find that it will cost more or less to produce an additional unit of a good.