Chris has a one-hour break between classes every Wednesday. Chris can either stay at the library and study or go to the gym and work out. The decision Chris must make is:

A.not an economic problem because it’s an hour that Chris has no matter what he does.

B.an economic problem because the tuition Chris pays covers the cost of both the gym and the library.

C.an economic problem because Chris has only one hour, and engaging in one activity means giving up the other.

D.not an economic problem because neither activity costs money.

正确答案：an economic problem because Chris has only one hour, and engaging in one activity means giving up the other.