The Student Center on Campus Has Burritos,bagels,or Burgers for Lunch,and

Multiple Choice

The student center on campus has burritos,bagels,or burgers for lunch,and they all cost the same.You love burgers and bagels,but you decide to have a burger today.If they were out of burgers,you would have bought a bagel.Which economic principle does this statement BEST represent?

A) The true cost of something is its opportunity cost.
B) "How much" is a decision at the margin.
C) One person's spending is another person's income.
D) There are gains from trade.