Final answer:
The economics chapter in question explores Principle 2, which focuses on opportunity cost and trade-offs, emphasizing the costs associated with every economic choice made.
Step-by-step explanation:
The principle of economics being explored in this chapter is Principle 2: The Cost of Something is What You Give Up to Get It. This principle addresses the concept of opportunity cost and trade-offs. Whenever a choice is made, such as deciding between going out on a Friday night or studying, there is a trade-off involved, and the opportunity cost is the next best alternative foregone. The scenario provided illustrates the idea that choosing one course of action includes foregoing others, and this concept is a critical part of economic decision-making.