The angle between two vectors $6 \hat{i} + 6 \hat{j} - 3 \hat {k}$ and $7 \hat{i} +4 \hat{j} + 4 \hat{k}$ is given by :

Question

( A ) $\cos^{-1} (\frac{5}{\sqrt{3}})$
( B ) $\sin^{-1} (\frac{\sqrt{5}}{3})$
( C ) $\sin^{-1} (\frac{2}{\sqrt{3}})$
( D ) $\cos^{-1}(\frac{1}{\sqrt{3}})$