According to Kirchhoff's voltage law, what must happen around any complete loop?

Kirchhoff's voltage law states that the sum of the electrical potential differences (voltages) around any closed loop in a circuit must equal zero. This means that when you traverse a complete loop in the circuit, the total gains in voltage (from sources like batteries) must be balanced by the total drops in voltage (across components like resistors, capacitors, etc.).

Therefore, the total voltage must add up to zero, reflecting the principle of conservation of energy – the energy supplied by the voltage sources is fully accounted for by the voltage drops across the other elements in the loop. This concept is crucial for analyzing and designing electrical circuits, as it helps ensure that energy is conserved within the system.

The other options do not align with this fundamental principle. For instance, stating that the total resistance must equal zero or that the total current must remain constant pertains to different electrical laws or concepts, but they do not capture the essence of Kirchhoff's voltage law.