For any vector $\overrightarrow{a}$,the value of $(\overrightarrow{a}.\hat i)^2+ (\overrightarrow{a}.\hat j)^2+ (\overrightarrow{a}.\hat k)^2$ is equal to

Question

$$(A)\;{\mid\overrightarrow{a}\mid}^2\quad(B)\;3{\mid\overrightarrow{a}\mid}^2\quad(C)\;4{\mid\overrightarrow{a}\mid}^2\quad(A)\;2{\mid\overrightarrow{a}\mid}^2$$