The emf generated by an AC generator (alternator) depends on the rotational speed ie., rotations per minute and the number of magnetic poles (South and North) placed around the rotor.
So A and B is the answer.
Formula for frequency of the AC current generated is :
f = p / 2 * N / 60 = p N / 120
N = rotations of rotor per minute
p = number of poles. like South, North pole, one pair means p = 2.