If a line makes angles of $\frac{3\pi}{4}$, $\frac{\pi}{3}$ and $\theta$ with the positive directions of $x$, $y$ and $z$-axis respectively, then $\theta$ is (A) $\frac{-\pi}{3}$ only (B) $\frac{\pi}{3}$ only (C) $\frac{\pi}{6}$ (D) $\pm\frac{\pi}{3}$