Microeconomics is the study of aggregate behavior in the economy.

A lighthouse is a public good

A) because it doesn't cost any more to light the way for 105 ships than it does to light the way for 104 ships, but for no other reason. B) because there is no way to prevent those who haven't contributed to the lighthouse from seeing better because of it, but for no other reason. C) because the government produces it, and for no other reason. D) for the reasons in A and B together. E) for the reasons in A, B, and C together.

In a repeated prisoner's dilemma, players:

A. can sustain cooperation by employing a tit-for-tat strategy. B. always play their dominant strategy. C. never learn to play their dominant strategies. D. can sustain cooperation by playing their dominant strategy.