The International Nickel Company of Canada Is Often Cited as an Example

The International Nickel Company of Canada is often cited as an example of monopoly. What was the source of the barrier to entry that gave this firm monopoly power?

A) It was a public enterprise; therefore, the Canadian government blocked entry into the market for nickel.
B) There were important network externalities in the production of nickel.
C) Economies of scale resulted in the company becoming a natural monopoly.
D) control of a key resource