Kirchhoff's loop rule states that the algebraic sum of changes in potential around any closed loop is zero. This rule is a consequence of

1. Electric potential has a definite value at each point in the circuit. 2. Going around a closed loop returns to the starting point. 3. The net change in a single-valued potential over a closed path must be zero. 4. So B; conservation of charge underlies the junction rule (A), not the loop rule. _Source: NCERT Class 12 Physics Ch 3 "Current Electricity", p.17_