Final answer:
The incorrect statement about competitive firms is that they can influence market prices. Competitive firms are price takers and must accept the market-determined price, with no individual firm having enough power to influence market prices.
Step-by-step explanation:
The statement which is not correct about competitive firms is: C) Competitive firms can influence market prices. In a perfectly competitive market, firms are considered to be price takers, which means they have no capability to influence the price of their products; instead, they must accept the equilibrium price determined by the overall market supply and demand. Competitive firms produce identical products, and there is easy entry and exit in the industry; thus, creating an environment where no single firm has market power. Moreover, in the long-run equilibrium of a perfectly competitive market, the entry and exit of firms ensure that economic profits are driven to zero, enforcing the price taker status of firms.