Suppose the 2- Firm Concentration Ratio (Measuring Output)in a Canadian

Suppose the 2- firm concentration ratio (measuring output) in a Canadian manufacturing industry is over 90%.Why might the market power of these 2 firms be less than the concentration ratio suggests?

A) A high concentration ratio usually indicates low degrees of market power.
B) A 2- firm concentration ratio does not provide enough information.
C) The product is purely domestic and there is no international trade.
D) The product is traded internationally and the two Canadian firms compete with many global rivals.
E) The relevant market is regional and so the concentration ratio is not relevant.