Which of the Following Would Be Considered a Fuel Cell $\rarr$

Which of the following would be considered a fuel cell

A) C₃H₈(g) + 5O₂(g) $\rarr$ 3CO₂(g) + 4H₂O(l)
B) Pb(s) + PbO₂(s) + 4H⁺(aq) + 2SO₄^2-(aq) $\rarr$ 2PbSO₄(s) + 2H₂O(l)
C) Zn(s) + 2NH₄⁺(aq) + 2MnO₂(s) $\rarr$ Zn²⁺(aq) + 2NH₃(aq) + H₂O(l) + Mn₂O₃(s)
D) Zn(Hg) + HgO(s) $\rarr$ ZnO(s) + Hg(l)
E) 2Fe(s) + O₂(g) + 4H⁺(aq) $\rarr$ 2Fe²⁺(aq) + 2H₂O(l)