The correct option is C. cost of producing a unit of output. Detailed Explanation: 1. Understanding Average Cost: Average cost (AC) is a key concept in economics that refers to the total cost of production divided by the number of units produced. It provides insight into how much it costs, on average, to produce each unit of output. The formula for calculating average cost is: [ \text{Average Cost (AC)} = \frac{\text{Total Cost (TC)}}{\text{Quantity of Output (Q)}} ] Where: - Total Cost (TC) includes both fixed costs (costs that do not change with the level of output, such as rent) and variable costs (costs that change with the level of output, such as materials and labor). - Quantity of Output (Q) is the total number of units produced. 2. Why Option C is Correct: Option C states that average cost is the "cost of producing a unit of output." This is accurate because average cost directly reflects the cost associated with producing each individual unit when total costs are spread over the total output. For example, if a company incurs a total cost of $1000 to produce 100 units, the average cost per unit would be: [ \text{AC} = \frac{1000}{100} = 10 ] This means it costs the company $10 to produce each unit of output. 3. Why Other Options are Incorrect:

• Option A: "the total cost of production"
• This option is incorrect because total cost refers to the overall expenditure incurred in producing goods, which includes both fixed and variable costs. Average cost, on the other hand, is derived from total cost but is not the same as total cost itself. Total cost does not provide information on the cost per unit.
• Option B: "the extra cost of producing one additional unit of output"
• This option describes marginal cost, not average cost. Marginal cost is the cost incurred by producing one more unit of a good or service. While marginal cost is an important concept in economics, it is distinct from average cost, which averages the total costs over all units produced.
• Option D: "variable cost"
• This option is also incorrect because variable cost refers specifically to costs that change with the level of output, such as raw materials and labor directly associated with production. Average cost encompasses both fixed and variable costs, making it a broader measure than variable cost alone.

Common Pitfalls:

• Confusing average cost with total cost or marginal cost is a common mistake. Remember that average cost is specifically about the cost per unit, while total cost is the sum of all costs, and marginal cost is about the cost of producing one additional unit.
• Not considering both fixed and variable costs when calculating average cost can lead to incorrect conclusions about production efficiency.

Revision Summary:

• Average cost is calculated as total cost divided by the quantity of output.
• It reflects the average expenditure per unit produced.
• It is distinct from total cost, marginal cost, and variable cost.
• Understanding the differences between these concepts is crucial for analyzing production costs effectively.