Explanation: When charging a DC battery, it's essential to connect the charger's positive terminal to the battery's positive terminal and the negative to the negative. If the polarity is reversed during charging, the external voltage forces current through the battery in the opposite direction. This reverse current can deplete the chemicals in individual cells beyond their normal discharge point, effectively driving their voltage into the negative range, causing them to become "reversed." This is damaging to the battery. * **A) Polarity was reversed while charging:** This correctly describes how a cell's voltage can become reversed. * **B) Polarity was doubled while charging:** "Doubling polarity" is not a standard electrical concept and does not explain reversed voltage. * **C) Polarity has no influence of charging:** This is fundamentally incorrect; polarity is critical for DC battery charging. * **D) Polarity was correct while charging:** Correct polarity would charge the battery normally, not reverse a cell's voltage.