A production possibilities frontier that is a downward-sloping straight line implies

It can be rational to play tit-for-tat in a repeated Prisoners' Dilemma game

A) only if the game is played an infinite number of times. B) if the game is played an infinite number of times, or if it is uncertain how many times it will be played. C) only if the game is played a finite number of times, and that number is known by all the players in advance. D) for n-1 of the n periods it will be played, if n is known in advance. E) at no time; tit-for-tat is an irrational strategy in this situation.

Quantitative evidence on federal land policy has led current economic historians to conclude that

a. the policy was inefficient and reduced total output. b. the policy was largely inefficient, with evidence of increased output only found on large farms. c. the Homestead Act allowed western farmers to enjoy rising agricultural prices for most of the post-bellum period. d. average rates of return on western agricultural investments were comparable to those in manufacturing.