Let R, F, L, B, T, U Mean Rotate 90°

Let R, F, L, B, T, U mean rotate 90° clockwise the right, front, left, back, top, and under faces, respectively. Name the move or moves that will return the cube to standard position after making the move B^-1. ​

A) F²
B) B²
C) B⁴
D) (B^-1) ²
E) B