Answer: The answer is A.
The total choices are calculated by the product of the options in each case.
here she has 5 types of stereos and 2 types of amplifiers, with this two items genevieve gets 10 combinations.
If we also add the speakers, let's suppose we get x options for the speakers, and the problem says that the total options are 30, so 10*x = 30
dividing by 10, we get x = 3.
so there are 3 options for speakers, and the correct answer is A.