In which type of market structure does a firm have no control over the price of its product and must accept the prevailing market price?

Introduction / Context:
Different market structures give firms different degrees of power over price. At one extreme, a monopoly can exercise substantial control, while at the other extreme a perfectly competitive firm has no control and must accept the market determined price. Understanding these differences is essential in microeconomics for analysing pricing behaviour, output decisions, and efficiency. This question checks whether you know which market structure corresponds to a firm that is a pure price taker.

Given Data / Assumptions:
- The question asks where a firm does not exercise control over price.
- The options list several market forms: mixed competition, monopoly, oligopoly, and perfect competition.
- We assume standard textbook definitions of these market structures.
- The focus is on pricing power, not on ownership or number of firms alone.

Concept / Approach:
In perfect competition, there are many small firms selling an identical or homogeneous product, and no single firm has any significant share of total market supply. As a result, each firm faces a perfectly elastic demand curve at the market price. If any firm tried to charge a price higher than the prevailing market price, buyers would simply switch to other sellers. Therefore, a perfectly competitive firm is a price taker. In monopoly, a single firm faces the entire market demand curve and can influence price by its output decision. In oligopoly, a few firms have significant market power and may engage in strategic pricing.

Step by Step Solution:
Step 1: Recall that a price taker is a firm that must accept the market price and cannot influence it by its own output choice. Step 2: Identify the market structure in which many small firms sell a homogeneous product and entry and exit are easy; this is perfect competition. Step 3: Option D explicitly states perfect competition, where many small firms are price takers, matching the concept. Step 4: Option B refers to monopoly, where one firm typically has significant control over price and is considered a price maker. Step 5: Option C refers to oligopoly, where a few firms may coordinate or compete in price setting and also possess some degree of market power. Step 6: Option A, mixed competition, is not a standard textbook market structure and does not specifically describe price taking behaviour.

Verification / Alternative check:
In a perfectly competitive agricultural market where thousands of farmers sell an identical crop, each farmer is too small to influence the overall market price. The market price is determined by the intersection of total market demand and total market supply. An individual farmer can choose how much to produce, but any additional output has a negligible effect on total supply and therefore on price. This real world example shows the essence of perfect competition and demonstrates why firms in this market form have no control over price, confirming option D as correct.

Why Other Options Are Wrong:
Option B is wrong because a monopolist is a price maker and can influence the price by changing its level of output; it has significant control over price.
Option C is wrong because firms in an oligopoly also have some control over price and often react strategically to the pricing decisions of rival firms.
Option A is wrong because mixed competition is not a standard market structure category and does not necessarily imply an absence of price control.

Common Pitfalls:
Students sometimes confuse the number of firms with price power and think that any market with many firms must be perfectly competitive. However, key conditions such as homogeneous products, free entry and exit, and perfect information are also necessary. It is also important not to assume that a firm always sets its own price; in perfect competition, the profit maximising choice is about output level at the given price, not about price setting. Remembering that perfect competition goes with price taking will help you answer similar questions quickly.

Final Answer:
Perfect competition, where many small firms are price takers.