Lời giải

Chọn B

Ta có: $\left\{ \begin{align}& {{x}_{O}}=\frac{{{x}_{A}}+{{x}_{B}}+{{x}_{C}}}{3} \\ & {{y}_{O}}=\frac{{{y}_{A}}+{{y}_{B}}+{{y}_{C}}}{3} \\ \end{align} \right.$.$\Leftrightarrow \left\{ \begin{align}& 0=\frac{-2+3+{{x}_{C}}}{3} \\ & 0=\frac{2+5+{{y}_{C}}}{3} \\ \end{align} \right.$$\Leftrightarrow \left\{ \begin{align}& {{x}_{C}}=-1 \\ & {{y}_{C}}=-7 \\ \end{align} \right.$