QUESTION $20$

The theory of contestable markets implies:

A$.$ The number of actual market competitors is relevant to the level of competitiveness.

B$.$ Potential competition is the same as actual competition when sunk costs are zero.

C$.$ Sunk costs have nothing to do with market contestability since sunk costs are in the past.

D$.$ The more sunk costs, the more hit and run entry tactics used by competitors.

E$.$ In a perfectly contestable market, a single seller behaves like a monopolist $($restricting output and raising price$).$