Answer:
(a) To draw water from a well we have to pull at the rope.
(b) A charged body attracts an uncharged body towards it.
(c) To move a loaded trolley we have to pull it.
(d) The north pole of a magnet repels the north pole of another magnet.
Explanation:
Just trust me
Net force is basically the force an object has when changing direction, so the answer would be D.