In voltaic cells, such as those diagrammed in your text, the salt bridge _______ .

In voltaic cells, such as those diagrammed in your text, the salt bridge _______ . (a) is not necessary in order for the cell to work (b) acts as a mechanism to allow mechanical mixing of the solutions (c) allows charge balance to be maintained in the cell (d) is tightly plugged with firm agar gel through which ions cannot pass (e) drives free electrons from one half-cell to the other