Instead of offering its products through "brick-and-mortar" companies, a book distributor decides to market directly to customers through the U. S. mail. This is an example of:
a. Disintermediation
b. Intensive distribution
c. Exclusive distribution
d. Franchising

a. Disintermediation          

Explanation:

Disintermediation: In finance, the term "disintermediation" is described as the withdrawal of a few specific funds associated with an "intermediary financial institutions", for example, loan associations and banks & savings in order to invest them directly. However, disintermediation generally happens when the inflation rates are being high yet bank interest rates are considered as stagnant and therefore depositors of the bank may receive a good return by investing in mutual securities and funds.

In the question above, the given statement represents disintermediation.