In a voltaic cell, the salt bridge acts to:

provide a direct contact between the oxidation and reduction electrodes

provide an input of energy for the oxidation half-reaction.

provide constant overall balanced concentration of ions.

provide a surface for oxidation and reduction to occur.

The salt bridge acts to maintain a constant ion concentration for both of the half-cells. The anions are moving toward the oxidation side and the cations are moving toward the reduction side via the salt bridge.

Therefore the answer is C- provide constant overall balanced concentration of ions.

explanation: