The correct answer is c) opportunity cost.
Opportunity cost refers to the value of the next best alternative that is foregone when making a choice. In simpler terms, whenever you decide to allocate resources to one option, there is something else you are giving up—whether it’s time, money, or other benefits. This concept is fundamental in economics because it encourages individuals and businesses to consider not just the cost of what they choose, but also what they are missing out on by not choosing the next best alternative.