The concept of opportunity cost refers to:

Opportunity cost is a fundamental concept in economics that measures the value of the next best alternative that is given up when a choice is made. When individuals, businesses, or governments make decisions, they must consider not only the explicit monetary costs but also what they are sacrificing by not choosing their next best option.

For instance, if someone decides to spend money on attending college instead of working full-time, the opportunity cost includes not only the tuition fees but also the income they could have earned during that time. This highlights the importance of considering both direct costs and forgone benefits when making economic decisions.

In contrast, the other choices refer to specific types of costs or elements in economics but do not capture the essence of opportunity cost. The cost of production is about the expenses incurred to produce goods, the overall cost of goods sold focuses on the calculation of all costs associated with selling products, and hidden costs of labor pertain to less visible aspects of employment expenses. None of these definitions embody the concept of opportunity cost, which is specifically about valuing the trade-offs that come with any decision-making process.