At 298 K a galvanic cell initially operates under standard conditions. As the reaction quotient Q steadily approaches the equilibrium constant K, which statement best describes the change in the cell potential E?
a) E increases in magnitude, reaching a maximum when Q=K.
b) E remains equal to E∘ until Q=K, then abruptly falls to zero.
c) E decreases in magnitude and becomes zero when Q=K.
d) E decreases, crosses zero, and becomes negative exactly when Q=K.