If $\overrightarrow{a}$ is a non-zero vector and $m$ is a non-zero scalar then $m\overrightarrow{a} $ is a unit vector if

Question

\[\begin{array}{1 1} (1)m=\neq\pm 1 &(2)a=| m | \\ (3)a=\large\frac{1}{|m|}& (4)a=1\end{array}\]