The kinetic energy of any body depends on the frame of reference of the observer. The kinetic energy is given by `1//2 mv_("rel")^(2)`. Similarly the displacement of the object from different frames of reference will be: different. But the forces acting on the body remain unchanged. So work done by the forces as seen from: different frames will be different. But work energy! theorem will still be hold in every inertial reference' frame.
For example, if a block of mass 2kg is moving with, velocity of `1m//s` towards east on a rough surface, its `KE = (1)/(2) xx 2 xx 1^(2) = 1J`
If it comes to rest, its `KE = 0`
work done by friction `= K_(f) - k_(i) = -1 J`
If we observe it form a frame 2 moving with `1m//s` toward east, its initial velocity will appear to be `1 - 1 = 0`
Initial `KE = (1)/(2) xx 2 xx 0^(2) = 0`
Final velocity `= 0 -1 = -1`
Final `KE = (1)/(2) xx 2 xx (-1)^(2) = 1J`
`rArr` Work done by friction `= 1 - 0 = 1J`
According to passage:

Options

A. In `2^(nd)` frame, force of friction was opposite to displacement
B. In `2^(nd)` frame, force of friction was in same direction as displacement
C. In ground frame, force of friction is in same direction as the displacement
D. None of the above

Answer

B