If $f: R \to R$ and defined by $f(x)=\large\frac{1}{2-\cos 3x}$ for each $ x \in R$, then the range of f is

Question

\[\begin {array} {1 1} (a)\;(1/3,1) & \quad (b)\;[1/3,1] \\ (c)\;(1,2) & \quad (d)\;[1,2] \end {array}\]