Why Is It Imperative That Manufacturers Like Hewlett-Packard and Procter

Why is it imperative that manufacturers like Hewlett-Packard and Procter & Gamble understand the operations of retailers?

A) To sell directly online
B) To encourage retailers to offer and promote their products
C) To develop strategies for selling without retailers
D) Retailers can expect fewer buyouts to occur
E) To have a wide assortment of products for customers to choose from