Which of the following statements is true for all voltaic (or galvanic) cells? [1]

(I) Reduction occurs at the cathode.
(II) The anode gains mass during discharge (note: this means operation of the cell.)
(III) The voltage is less than or equal to zero.

(a) only III (b) only II (c) only I (d) II and III (e) I, II, and III