Kirchhoff's second law is based on the law of conservation of

The correct answer is Option (2) → Energy

Kirchhoff's second law (loop rule) says that the algebraic sum of the potential differences around any closed loop is zero. The potential difference is the work done per unit charge, so taking a charge round a closed loop and back to its starting point gives no net gain or loss of energy. The loop rule is therefore a statement of conservation of energy.

Option (1) Momentum — Incorrect. Momentum does not enter circuit laws.

Option (2) Energy — Correct. The loop rule expresses conservation of energy.

Option (3) Charge — Incorrect. Conservation of charge is the basis of the first law (junction rule).

Option (4) Mass — Incorrect. Mass conservation plays no part in Kirchhoff's laws.

Note: A similar question was also asked in CUET (UG) 2023 on 02-07-2023 (Slot 3).