Underline the correct alterntaive:
a) when a conservative force does positivie work on a body, the potential energy of the body increase/decreases/remains unaltered.
work done by a body against friction always results in a loss of its kinetic /potential energy.
c) The rate of change of total momentum of a many-particle system is proportional to the external force/ sum of the internal forces on the system.
d) In an inelastic collision of two bodies, the quantities which do not change after the collision are the total kinetic energy/total linear momentum/total enregy of the system of two bodies.

Explanation

External force