What balances charges that may build up as reduction and oxidation occur in a voltaic cell?

a.

the salt bridge

c.

the electrolyte solutions

b.

one of the half-cells

d.

the moving electrons

I think the correct answer from the choices listed above is option A. It is the salt bridge that balances charges that may build up as reduction and oxidation occur in a voltaic cell. The salt bridge is to maintain charge balance because the electrons are moving from one half cell to the other.