The radius is simply half of the diameter, so you would divide 25 by two. This gives you 12.5, and since the question does not specify to round your answer, I believe the answer would be that none are correct.
I am pretty sure the answer would be none of these choices are correct, because the radius of a circle is half of the diameter. Since the diameter is 25 the radius would have to be 12.5. hope this helps.
