It should be S since S stands for students. Giving the team with more members the upper hand. Hope this helps.
I'm sorry if my answer is too late but they didn't provide the letter S as a variable to represent the students. If that were the answer they would have specifically provided that information in the question. I'm a student of K12 as well so I can confirm that the answer is
B)The overall mass of the team.
Have a nice day!
