B is your answer.
Because 7 times 8 is 56 and 7 times 3 is 21.
The theorical probability is 1/4, because there are 4 possible outcome, and they are equally likely to be picked (the sectors have the same area)
The experimental probability is 3/20, becuase the red sector was picked 3 times in 20 trials.
Eight is the greatest common factor because it is the last of the numbers that can go into both of those numbers.
The answer is D.
The others equal 90
