The Prisoner's Dilemma Game Is an Excellent Vehicle for Studying

The Prisoner's Dilemma game is an excellent vehicle for studying social conflicts in the laboratory because

A) researchers can systematically vary the strategies participants use.
B) there are clear winners and clear losers,and thus reliable dependent variable measures.
C) there is one and only one right answer to the problem.
D) the rules of the game pit self-interest against looking out for someone else's interest.
E) the variables of the game are clearly defined.