You might want to look at the Master Theorem
In the wiki, a = 1, b = 2, c = 2, where T(n) = aT(n/b) + n^c
Case 3 applies, since 2 > 0 = log_2(1)
Thus, by the master theorem, T = Big-Theta(n^c) = Big_Theta(n^2).
Choice B has a n^2 term, so that should be your answer.