Consider the following complex numbers
\[
\begin{array}{l}
z_{1}=r_{1}\left(\cos \theta_{1}+i \sin \theta_{1}\right) \\
z_{2}=r_{2}\left(\cos \theta_{2}+i \sin \theta_{2}\right)
\end{array}
\]
where $r_{1}, r_{2}$ are real numbers, $0 \leq \theta_{1} \leq \dfrac{\pi}{2}, 0 \leq \theta_{2} \leq \dfrac{\pi}{2}$, and $i=\sqrt{-1}$
If $\left|z_{1}+z_{2}\right|=\left|z_{1}\right|+\left|z_{2}\right|$, which one of the following conditions is necessarily CORRECT?
- $\theta_{1}=0, \theta_{2}=\dfrac{\pi}{2}$
- $\theta_{1}=\dfrac{\pi}{2}, \theta_{2}=0$
- $r_{1}=r_{2}$
- $\theta_{1}=\theta_{2}$
