Let's run down the list of answers and figure out which numbers work.
1^2 is 2, 2 - 9 = -7, so not A.
-3^2 is -9, -9 - 9 = 0, so not B.
2^2 is 4, 4 - 9 = -5, so not C.
-2^2 is -4, -4 - 9 = -13, so not D.
3^2 is 9, 9 - 9 = 0, so E is one answer.
-1^2 is -1, -1 - 9 = -10, so not F.
So, E will be your answer. Hope that helps!