When you sit still in a chair with your feet on the ground and your back pressing against the back of the chair, are the forces acting on you balanced? explain. are the forces acting on you balanced if you lift your feet off the floor but remain still? explain. lastly, if you tilt back in your chair (not recommended! ) and you fall backwards to the floor, are the forces acting on you balanced while you are falling? explain. how about after you have hit the floor? explain.

Yes, the forces are balanced, gravity pulling you down and normal force supporting you up.     The same works if you are holding your feet up only difference would be that you would have no normal force supporting your feet but more normal force supporting you at your bottom.
As you are falling you now have unbalanced force, the force of gravity pulling you down is greater than the forces holding you from moving (pretty much just a little bit of drag (air resistance)
Once you come to rest on the floor and stop the forces are balanced once again as the force of gravity pulling you down is equal to the normal force of the floor supporting you.

The correct answer is c