A galvanic cell is a cell which converts chemical energy liberated in a redox reaction to electrical energy. If an externally opposite potential is applied in a slowly increasing manner to the cell, the reaction continues to occur till the potential difference is equal to the value of the cell’s potential. Then, the reaction stops and no current flows through the cell. Further increase in the potential leads to the start of the reaction again but in the opposite direction, making it function as an electrolytic cell which is a cell for using electrical energy to drive non-spontaneous chemical reactions. The correct option is (iii).