Let each box having a question mark be x. The sum of the boxes at the top and bottom would be equal to the total number of freshmen and sophomores. Thus, we have
x + 2x + 6 = 39
3x + 6 = 39
3x = 39 - 6 = 33
x = 33/3
x = 11
Thus, the number of sophomores would be
11 + 11 + 6
= 28
The correct option is A
