If $z_1\:\:and\:\:z_2$ are two complex numbers such that $|z_1+z_2|=|z_1|+|z_2|$, then $argz_1-argz_2=?$

Question

$\begin{array}{1 1}(A) \; \pi\\(B)\;\large\frac{\pi}{2}\\(C)\;-\large\frac{\pi}{2}\\(D)\; 0 \end{array}$