The correct answer would be A) 80 because if we organize all the tests scores from smallest numbers to biggest, and cross out numbers from each side, and keep going till one is left, we see 80 is the last number in the middle. *below is a image of my work.
Then, you work out how many balls are needed: 30 can fit into 102.4 3 times with .41m to spare. So, you need three balls of string, PLUS another one to cover the 41cm