Assume Beth's friends want to take her to a movie or a play for her birthday. Beth chooses to attend the play. We know that:
A.
Beth has made an irrational decision.
B.
not seeing the movie is Beth's opportunity cost of attending the play.
C.
Beth did not make a decision at the margin.
D.
seeing the play did not cost Beth anything since she did not have to pay for the ticket.