In the Properly Balanced Half-Reaction (Acid Solution) for the System

In the properly balanced half-reaction (acid solution) for the system H₃AsO₃→H₂AsO₄ ^- , what else appears on the right side besides H₂AsO₄ ^- ?

A) 2 H⁺ + 2 e ^-
B) 3 H⁺ + 2 e ^-
C) 2 H₂O + 2 e ^-
D) 2 H⁺ + 3 e ^-
E) H⁺