Which reaction represents water gas shift reaction?

1.
Which reaction represents water gas shift reaction?

1. 2. 3. 4.

1. A(g)  A2+(g) + 2e–2. A(s)  A+(g) + e–3. A(g)  A+(g) + e–4. A2(g)  A+(g) + e–

1. Pb + CuSO4 → PbSO4 + Cu2. Zn + NiSO4 → ZnSO4 + Ni3. Na + CaSO4 → Na2SO4 + Ca4. K + CaSO4 → K2SO4 + Ca