Question

The work done by all the forces (external and internal) on a system equals the change in
(a) total energy
(b) kinetic energy
(c) potential energy
(d) none of these

Answer 1

Answer ⇒ Option (b). Kinetic Energy.

Explanation ⇒ As we know that the work done by the external force changes into the total energy but the internal force acting in the object can only vibrates the molecules or the atoms which in further leads to the movement as the result of which Kinetic energy also increases. 
Thus, the work done by all the forces (External or Internal)  will completely leads to the increases in the kinetic energy. 

Hence, Option (b) is correct.
 

Hope it helps.

Answer 2

yes the option b is correct kinetic energy