The correct option is C. the law of diminishing returns. Explanation of the Correct Answer The law of diminishing returns, also known as the principle of diminishing marginal returns, is a fundamental concept in economics that describes how the addition of a variable input (in this case, labor) to a fixed input (land, in this scenario) will eventually yield lower incremental increases in output. Step-by-Step Explanation:

1. Understanding Inputs and Outputs:
2. In production, we often have fixed inputs (like land) and variable inputs (like labor). When we keep one input constant and increase the other, we can observe how output changes.
3. Initial Increases in Output:
4. When the first few units of labor are added to a fixed amount of land, the output increases significantly. This is because the additional workers can utilize the land more effectively, leading to higher productivity.
5. Point of Diminishing Returns:
6. As more units of labor are added, there comes a point where each additional worker contributes less to total output than the previous worker. This is the essence of the law of diminishing returns. For example, if the first worker can produce 10 units, the second might produce 12, but the third might only produce 8, and so on.
7. Why This Happens:
8. The reason for this phenomenon is that while labor is increasing, the amount of land (a fixed input) does not change. Eventually, the land becomes overcrowded with workers, leading to inefficiencies. Workers may get in each other's way, or there may not be enough tools or space for everyone to work effectively.
9. Graphical Representation:
10. If you were to graph this scenario, you would see a curve that initially rises steeply (indicating increasing returns) and then begins to flatten out (indicating diminishing returns). The point where the curve starts to flatten is where diminishing returns set in.

Explanation of Why Other Options Are Incorrect:

• A. the productivity of labour:
• While this term refers to the output produced per unit of labor, it does not specifically address the concept of diminishing returns. Productivity can increase or decrease, but the law of diminishing returns specifically focuses on the incremental output from adding more labor to a fixed resource.
• B. the law of diminishing marginal utility:
• This law pertains to consumer behavior and states that as a person consumes more units of a good, the additional satisfaction (utility) gained from each additional unit decreases. It is not related to production processes or the relationship between labor and fixed inputs.
• D. the concept of factor intensity:
• Factor intensity refers to the ratio of different factors of production (like labor and capital) used in the production process. It does not specifically address the diminishing returns of adding labor to a fixed amount of land.

Common Pitfalls:

• Students often confuse the law of diminishing returns with the law of diminishing marginal utility. Remember, the former deals with production and inputs, while the latter deals with consumption and satisfaction.
• It’s important to recognize that diminishing returns only occur when one input is fixed while another is variable. If all inputs are variable, this law does not apply.

Revision Summary:

• The law of diminishing returns states that adding more of a variable input (like labor) to a fixed input (like land) will eventually yield smaller increases in output.
• Initially, output increases significantly, but as more labor is added, the additional output from each new worker decreases.
• This concept is crucial in understanding production efficiency and resource allocation in economics.