Explanation: Nickel-cadmium (NiCd) cells, due to their specific internal chemistry involving nickel and cadmium electrodes with an alkaline electrolyte, produce a nominal operating voltage of approximately 1.25 volts per cell. This voltage remains relatively stable over a large portion of their discharge cycle. Options B, C, and D are incorrect because they represent the nominal voltages of different battery chemistries: * **1.4 volts** is close to the peak charging voltage for NiCd, but not its nominal operating voltage. * **1.5 volts** is the common nominal voltage for alkaline or carbon-zinc cells. * **2.1 volts** is the nominal voltage for a single lead-acid cell.