Choose the correct answer in the following : let \( \overrightarrow a\) and \( \overrightarrow b\) be two unit vectors and θ is the angle between them. Then \( \overrightarrow a\ + \overrightarrow b\) is a unit vector if

Question

\[ \begin{array} (A)\; \theta = \frac{\pi}{4} \quad & (B)\; \theta = \frac{\pi}{3} \quad & (C) \;\theta = \frac{\pi}{2} \quad &(D) \;\theta = \frac{2\pi}{3} \end{array} \]