Which of the problems listed will occur if a lead-acid battery is allowed to remain in a discharged condition for a long period of time?

Correct Answer: Option D — The battery may be unable to accept a full charge.

Leaving a lead-acid battery in a discharged state promotes the formation of hard, crystalline lead sulfate on the plates. This process, known as sulfation, reduces the active surface area and internal porosity, eventually rendering the battery unable to accept or hold a full charge during subsequent recharge attempts.