A small block of mass `m` is released from a fixed smooth wedge in figure. Initial point is marked as `A`. Bottom of wedge is marked as `B` and at a point `C` the block stops because the straight part of floor is rough.
Work donw by normal reaction is zero during the motion of the block
A. from point `A` to `B` only
B. from point `B` to `C` only
C. from `A` to `C`
D. none of these