Which equation represents the second electron affinity of oxygen?

A.     \(\frac{1}{2}{{\text{O}}_2}{\text{(g)}} + {\text{2}}{{\text{e}}^ - } \to {{\text{O}}^{2 - }}{\text{(g)}}\)

B.     \({\text{O(g)}} + {\text{2}}{{\text{e}}^ - } \to {{\text{O}}^{2 - }}{\text{(g)}}\)

C.     \({{\text{O}}_2}{\text{(g)}} + {\text{4}}{{\text{e}}^ - } \to {\text{2}}{{\text{O}}^{2 - }}{\text{(g)}}\)

D.     \({{\text{O}}^ - }{\text{(g)}} + {{\text{e}}^ - } \to {{\text{O}}^{2 - }}{\text{(g)}}\)

D