Which of the Following Is Most Likely to Exert the Bargaining

Which of the following is most likely to exert the bargaining power of a buyer?

A) Barnes and Noble purchases books from publishers for sale in its online stores.
B) Wal-Mart, the world's largest discount store, seeks vendors to supply products made exclusively for its stores.
C) Ground beef producers seek to purchase cattle from ranchers.
D) Cowgirl Creamery, a small cheese producer, seeks a dairy farm for its organic milk supplies.