Explanation: Sulfation is the formation of hard, non-conductive lead sulfate crystals on the plates of a lead-acid battery, often occurring when batteries are left discharged or undercharged for extended periods. A) These sulfate crystals inhibit the chemical reactions essential for producing electricity. This reduces the amount of active material available, leading to a noticeable drop in the battery's terminal voltage, especially under load. B) The sulfate acts as an insulator, physically blocking the electrolyte from reaching the battery plates and impeding the flow of electrons. This directly increases the battery's internal resistance, making it less efficient at delivering current. C) With reduced terminal voltage and increased internal resistance, the battery's ability to supply current and maintain voltage under load is severely degraded. Since power output is a function of both voltage and current (P = V x I), a battery affected by sulfation will exhibit significantly reduced power output. Therefore, all the listed effects are direct consequences of sulfation, making "D) All of the above" the correct answer.