Me w this one multiple choice question (principles of business (p. o.b.)

Which of the following is the best example of substitution? a. movie producers begin making more comedies because they cost less to make than action films. b. people walk out before the end of a movie because the acting and the plot are terrible. c. people at the movie theater switch from popcorn to candy because popcorn has gotten too expensive. d. more people begin going to matinee movies instead of night movies to save money on the tickets.