Which of the following is NOT a barrier to entry?

Part 2

A.

Spectrum Cable has a network of cable throughout Durham, North Carolina, allowing them to provide cable TV and internet service to households at a very low marginal cost and a lower average total cost than its competitors.

B.

Netflix streams many newly released movies.

C.

Moderna is the only firm legally allowed to produce and sell its coronavirus vaccine.

D.

Alcoa owns a majority of the world's bauxite mines.