Which of the Following Is True

Which of the following is true?

A) Concentration ratios take into account competition from substitute goods.
B) The four-firm concentration ratio is likely to be larger than the eight-firm concentration ratio.
C) There are assumed to be insignificant barriers to entry in the theory of oligopoly.
D) A designer label on a pair of jeans is a way of differentiating one seller's jeans from another seller's jeans.
E) all the above