If $\theta$ is the angle between the vectors $\overrightarrow a$ and $\overrightarrow b$, and $|\overrightarrow a.\overrightarrow b|=|\overrightarrow a\times\overrightarrow b|$, then $\theta$=?

Question

$\begin{array}{1 1} 0 \\ \large\frac{\pi}{4} \\\large\frac{\pi}{3} \\ \large\frac{\pi}{3} \\ \large\frac{\pi}{2} \end{array}$