Students read a book about the opportunity costs of starting a business, play a fill-in-the-blank game, and discuss things they could give up so they can have something else. Big idea: When we choose to do or buy one thing, we often have to give up something else. Topic: Earn (Becoming an entrepreneur, Learning about careers, Making money), Spend (Buying things). School subjects: CTE (Career and technical education), English or language arts, Social studies or history.