For economists, every decision is made by knowledge of what one must forgo-in terms of money and enjoyment-in order to take it up. By knowing precisely what you are receiving and what you are missing out on, you ought to be able to make better-informed, more reasonable decisions. Consider that most famous economic rule of all: there's no such thing as a free lunch. Even if someone offers to take you out to lunch for free, the time you will spend in the restaurant still costs you something in terms of forgone opportunities.

　　Some people find the idea of opportunity cost extremely discouraging: imagine spending your entire life calculating whether your time would be better spent elsewhere doing something more profitable or enjoyable. Yet, in a sense it's human nature to do precisely that-we assess the advantages and disadvantages of decisions all the time.

　　In the business world, a popular phrase is "value for money. "People want their cash to go as far as possible. However, another is fast obtaining an advantage:"value for time. "The biggest restriction on our resources is the number of hours we can devote to something, so we look to maximize the return we get on our investment of time. By reading this passage you are giving over a bit of your time which could be spent doing other activities, such as sleeping and eating. In return, however, this passage will help you to think like an economist, closely considering the opportunity cost of each of your decisions.

1. According to the passage, the concept of "opportunity cost" is applied to　　.

A. making more money

B. taking more opportunities

C. reducing missed opportunities

D. weighing the choice of opportunities

2. The "leftover. . . time" in Paragraph 3 probably refers to the time　　　.

A. spared for watching the match at home

B. taken to have dinner with friends