In the long run, all factors of production are variable.
Factors of production are the resources that are used to produce goods and services. They include land, labor, capital, and entrepreneurship. In the short run, some factors of production may be fixed, meaning that they cannot be easily changed, while others are variable, meaning that they can be adjusted in response to changes in demand.
However, in the long run, all factors of production are variable because firms have more flexibility to adjust their production processes. For example, a firm may be able to expand its factory or hire more workers in the long run to increase production in response to higher demand. Similarly, a firm may be able to reduce its production capacity in the long run if demand falls.
In the long run, firms have more time to make adjustments to their production processes and can choose to change any of the factors of production in order to optimize their operations. This makes all factors of production variable in the long run.
In summary, in the long run, all factors of production are variable because firms have more flexibility to adjust their production processes and can change any of the factors of production in order to optimize their operations.