If the complex numbers $z_1,\:z_2,\:z_3$ represent the vertices $A,\:B,\:C$ of a parallelogram, then the fourth vertex $D$ is ?

Question

$\begin{array}{1 1}(A)\large\frac{1}{2}(z_1+z_2) \\ (B) z_1-z_2+z_3\\ (C)\large\frac{1}{2}(z_1+z_3) \\(D) \large\frac{1}{2}(z_2+z_3) \end{array}$