If There Are So Many Advantages to Selling National Brands

If there are so many advantages to selling national brands, why do retailers still carry private-label brands?

A) Private-label brands yield higher profits to retailers.
B) Private-label brands require less investment for a retailer from design to display.
C) Customers have loyalty to national brands.
D) National brands have better quality overall than private-label brands.
E) National brands offer a retailer more flexibility on how merchandise is displayed and advertised.