Concept:The formation of hydrogen bubbles on the copper plate of a primary cell is called polarization.Explanation:During operation of a primary cell, hydrogen bubbles form and cling to the copper plate, which acts as the positive electrode.These bubbles create a thin layer of hydrogen gas over the copper plate.This hydrogen film increases the internal resistance of the cell.It also reduces the electromotive force (e.m.f.) of the cell, making it inactive quickly.This effect is known as polarization.Answer:A. polarization.