In college chemistry, battery symbols are written (from left to right): negative electrode, salt bridge and positive electrode. The salt bridge separates the anode and cathode with double vertical lines, as shown in the figure.

In the primary battery, the negative electrode means losing electrons and the positive electrode means gaining electrons, so the problem should be that the electrons are lost in the first half, that is, Fe2+ becomes Fe3+; The electron in the second half, that is, Ce4+ becomes Ce3+; That is, Fe2+ is used as reducing agent and Ce4+ is used as oxidizing agent. According to the above information, you should choose B.

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