Fred and Ann Are Both Given Free Tickets to See

Fred and Ann are both given free tickets to see a movie. Both decide to see the same movie. We know that

A) the opportunity cost of seeing the movie is zero because the tickets were free.
B) both bear an opportunity cost of seeing the movie because they could have done other things instead of seeing the movie.
C) it is not possible to calculate the opportunity cost of seeing the movie because the tickets were free.
D) both bear the same opportunity cost of seeing the movie because they are doing the same thing.