The quantity which must be added to `(1-x) (1+x^(2))` to obtain `x^(3)` is

Options

A. `2x^(3)+3x^(2)+x+1`
B. `2x^(3)+x^(2)+x-1`
C. `2x^(3)-x^(2)+x-1`
D. `-x^(2)+x-1`