Which of These Must Be TRUE of a Prisoner's Dilemma

Which of these must be TRUE of a prisoner's dilemma outcome?

A) There exists no other outcome that is better for both players.
B) There is no opportunity to collude or cooperate to improve both players' payoffs.
C) It is a Nash equilibrium resulting from each player using its best-response strategies.
D) Neither player has a dominant strategy in the game.