Final answer:
The correct expression of the law of diminishing returns is that as we add more units of a variable input to a fixed input, the marginal product of this variable input will eventually decrease. This principle is evident in various scenarios such as agricultural production, where too much water can eventually decrease crop yield.
Step-by-step explanation:
The law of diminishing returns states that as more units of a variable input are added to a fixed input, the marginal product of the variable input will eventually decrease. This concept is a key principle in economics, particularly when considering production processes. The law reflects a point at which the addition of resources contributes less to overall output.
An example to illustrate this concept is the irrigation of a crop: a farmer's field (a fixed input) is watered (variable input) to increase crop yield. Initially, as more water is added, the output substantially increases. However, beyond a certain point, adding more water results in smaller yield increases, and if continued, may even lead to a decrease in output due to flooding. Therefore, in this case and in accordance with the marginal analysis, the marginal product diminishes as each additional unit of water contributes less to the crop yield.
The correct answer to the question is option 1: 'As more units of a variable input are added to a fixed input, the marginal product of the variable input will eventually decrease.'