Kirchhoff's second law for an electric network is based on:

Law of conservation of energy

The correct answer is Option (3) → Law of conservation of energy

Kirchhoff’s second law (loop or voltage law) states that the algebraic sum of all potential differences in any closed loop of an electrical circuit is zero.

This is based on the law of conservation of energy, since the total energy gained per unit charge is equal to the total energy lost per unit charge around the loop.

Answer: Law of conservation of energy