To economists, the main difference between the short run and the long run is that Multiple Choice in the short run all resources are fixed, while in the long run all resources are variable. fixed costs are more important to decision making in the long run than they are in the short run. in the long run all resources are variable, while in the short run at least one resource is fixed. the law of diminishing returns applies in the long run, but not in the short run.

The correct answer is letter "C": in the long run all resources are variable, while in the short run at least one resource is fixed.

Explanation:

When talking about marginal costs, the short-run cost vary according to the quantity of goods being produced. In the long run, the variation of quantities is considered for all the inputs necessary for the production of the goods. The main difference between both of them is that in the long run there are no fixed factors.

Answer: In the long run all resources are variable while in short run at least one is fixed.

Explanation: In the short run the firms in the industry make their profits in a relatively short period of time and then leave, thus, at least one factor in the firm stays fixed as the need to raise it more do not arise in that time period.

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While in the long run the firm gets affected from the economic activities, thus, they have to adjust every factor like capital, labor and land as per the requirements, so every factor is variable in long run.