Find the sine of the angle between the vectors $\overrightarrow{a}=3\hat i+\hat j+2\hat k$ and $\overrightarrow{b}=-2\hat i+2\hat j+4\hat k.$

Question

$\begin{array}{1 1} (A)\;\large\frac{4 \sqrt 5}{\sqrt {21}} \\(B)\;\large\frac{2 \sqrt 5}{21} \\ (C)\;\large\frac{2 \sqrt 5}{\sqrt {21}} \\ (D)\;\large\frac{8 \sqrt 5}{\sqrt {21}}\end{array}$