Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

(N/A) When a pendulum bob is displaced to one side (point $B$ or $C$) and released,it oscillates about its mean position $(A)$.
At the extreme positions ($B$ and $C$),the bob is at its maximum height,so its potential energy $(P.E.)$ is maximum and kinetic energy $(K.E.)$ is zero. As it moves towards the mean position $(A)$,$P.E.$ decreases and $K.E.$ increases. At the mean position $(A)$,the bob is at its lowest point,so $P.E.$ is zero and $K.E.$ is maximum. Throughout the motion,the total mechanical energy $(P.E. + K.E.)$ remains constant,illustrating the law of conservation of energy.
The bob eventually comes to rest because of air resistance,which opposes its motion and does work against it.
Its energy is eventually dissipated into the surroundings as heat energy due to friction with air molecules.
No,this is not a violation of the law of conservation of energy. The energy is not lost; it is merely transformed into other forms (heat and sound) in the surroundings,keeping the total energy of the system and its surroundings constant.