Option 1 -> Total Cost is the sum of all costs incurred by the firm and is not equal to price or marginal revenue.
Option 2 -> Marginal Cost equals price only at the profit-maximizing output level (P=MC condition), not universally.
Option 3 -> Total Revenue is price multiplied by quantity (TR = P × Q), not equal to price itself.
Option 4 -> Average Revenue is Total Revenue divided by quantity (AR = TR/Q = P), which always equals the price for any firm.
Hence, Option 4: Average Revenue -> For a price-taking firm in perfect competition, the market price remains constant regardless of output. Since Marginal Revenue is the additional revenue from selling one more unit, it equals the market price (MR = P). Similarly, Average Revenue (total revenue divided by quantity) also equals the price (AR = TR/Q = P×Q/Q = P). Therefore, for a price-taking firm: Price = Marginal Revenue = Average Revenue. This is a fundamental characteristic of perfectly competitive markets. -> correct