Australian Grocery Retailers Woolworths and Coles Operate in What Could

Australian grocery retailers Woolworths and Coles operate in what could be described as an oligopoly. This situation exists when:

A) there is only one buyer.
B) there is only one supplier and there are significant barriers to new competitors.
C) numerous competitors offer undifferentiated products.
D) numerous competitors offer similar products, prompting the competitors to strive to make their products unique from others.
E) there are a small number of competitors offering similar, but somewhat differentiated, products and there are significant barriers to new competitors.