I believe the answer is not b, because for equilibrium to occur there cannot be genetic drift. I believe the answer is not a, because gene flow is not allowed under hardy weinberg equilibrium. I believe the answer is not D, because a, and b, which are not right answers, all talk about genetic changes occuring. Since D is also a genetic change, I would say the answer is
C. Random mating occurs, which is one of the conditions to create hardy weinberg equilibrium
