B is indeed wrong.
The incline shown on the right in B will indeed be black. However, the 2 "steps" will be white as you see 2 white squares attached to the black strip in the unfolded portion.. The top will be white, and a portion of the shape above the black incline will be white as well.
Also, the first block on the right face of the figure should be black as shown in A and D, eliminating B and C.
Hope that helps.