A Certain Electrochemical Cell Has for Its Cell Reaction: Zn $\to$

A certain electrochemical cell has for its cell reaction: Zn + HgO $\to$ ZnO + Hg
Which is the half-reaction occurring at the anode?

A) HgO + 2e^- $\to$ Hg + O^2-
B) Zn²⁺ + 2e^- $\to$ Zn
C) Zn $\to$ Zn²⁺ + 2e^-
D) ZnO + 2e^- $\to$ Zn