Multiple Choice If $z_{1}=r_{1} e^{i \theta_{1}}$ and $z_{2}=r_{2} e^{i \theta_{2}}$ are complex numbers, then $\frac{z_{1}}{z_{2}}, z_{2} \neq 0,$ equals:
(a) $\frac{r_{1}}{r_{2}} e^{i\left(\theta_{1}-\theta_{2}\right)}$
(b) $\frac{r_{1}}{r_{2}} e^{i\left(\theta_{1} \cdot \theta_{2}\right)}$
(c) $\frac{r_{1}}{r_{2}} e^{i\left(\theta_{1}+\theta_{2}\right)}$
(d) $\frac{r_{1}}{r_{2}} e^{i\left(\theta_{1} / \theta_{2}\right)}$