The Best-Selling Mystery to the Nines by Janet Evanovich Was

The best-selling mystery To the Nines by Janet Evanovich was sold in hardcover for $25.95 when it was released. One year later, the publisher issued a softcover edition for $7.99. If the marginal cost of printing a softcover book is not much less than the marginal cost of printing a hardcover, the pricing difference:

A) cannot be explained by economic theory.
B) is probably due to price discrimination in which the seller charges a higher price to consumers with a more elastic demand.
C) is probably due to price discrimination in which the seller charges a higher price to consumers with less elastic demand.
D) must be due to a difference in fixed costs.