Let the vector \(\vec{a} \; and\; \vec{b}\) be such that \(|\vec{a}| = 3\; and\; |\vec{b}| = \frac{\sqrt{2}}{3},\; then\; \vec{a}\times\vec{b}\) is a unit vector ,if angle between \(\vec{a} \; and\; \vec{b}\) is
(A) \(\frac{\pi}{6}\)
(B) \(\frac{\pi}{4}\)
(C) \(\frac{\pi}{3}\)
(D) \(\frac{\pi}{2}\)