Under What Circumstance Is There a Mixed Nash Equilibrium for the Hawk-Dove

Under what circumstance is there a mixed Nash equilibrium for the hawk-dove game?

A) when the cost of fighting equals the benefit of a victory
B) when the cost of fighting is greater than the benefit of a victory
C) when the strategy of the other player is unknown and the game is played multiple times
D) when all members of the population play hawk exclusively