Explanation: Lead-acid storage cells, a common power source in amateur radio for station backup and mobile operations, have a nominal voltage of 2 volts per cell. When fully charged, the electrochemical reaction within the cell yields a slightly higher open-circuit voltage. This potential typically measures between 2.06 and 2.2 volts per cell, with 2.06 volts representing a common average for a fully charged state at rest. Options A (1 volt) and B (1.2 volts) are far too low for a lead-acid cell; 1.2 volts is characteristic of Nickel-Cadmium (NiCd) or Nickel-Metal Hydride (NiMH) cells. Option C (1.56 volts) is also incorrect, as this voltage is typical of single-use alkaline or carbon-zinc cells. Understanding these specific voltages is crucial for proper battery charging, monitoring, and application in amateur radio.