Ta chọn câu B
\(2x+\left(y-3\right)i=-x+3-\left(3y-5\right)i\)
\(\Leftrightarrow \left\{\begin{array}{l} {2x=-x+3} \\ {y-3=-\left(3y-5\right)} \end{array}\right. \Leftrightarrow \left\{\begin{array}{l} {x=1} \\ {y=2} \end{array}\right. .\)
Vậy \(S=x^{2} +y^{{}^{2} } =1^{2} +2^{2} =5.\)