Final answer:
The situation that best describes an opportunity cost is B, where a person decides to go back to college, as they give up possible income and career opportunities to pursue education. Opportunity cost is the next best alternative given up when making a decision.
Step-by-step explanation:
Opportunity cost is a fundamental principle of economics that represents what one must give up to obtain what he or she desires. It is essentially the value of the next best alternative foregone as a result of making a decision. Among the given scenarios, situation B, where a person decides to go back to college to transition into a new career, best describes opportunity cost. This is because they are potentially giving up their current employment income and the possible opportunities that come with it to pursue a different long-term goal. The cost of their education and the time invested in it represent the opportunities forgone, such as continuing to earn a salary or gaining more experience in their current field.
Contrast this with the other scenarios, A and C do not represent a trade-off of a foregone alternative but are the results of business activities, and D describes a situation of limited resources but not the opportunity cost to the employer herself.