In the Ultimatum Game, One Reason Players Don't Choose the Rational

Multiple Choice

In the ultimatum game, one reason players don't choose the rational offer is

A) that there are too many possible outcomes to reasonably consider.
B) they are worse off by taking the offer.
C) most people believe in reciprocity, and will therefore get even if the prosper treats them badly.
D) that it is not a Nash equilibrium.