b
\([{C^2}LR]\) \(= \left[ {{C^2}{L^2}\frac{R}{L}} \right]\) \(=\left[ {{{(LC)}^2}\left( {\frac{R}{L}} \right)} \right]\)

\(f = \frac{1}{{2\pi }}\frac{1}{{\sqrt {LC} }}\)

\(LC = [{T^2}]\, \frac{L}{R} = [T]\). \(\left[ {{{(LC)}^2}\left( {\frac{R}{L}} \right)} \right]\, \) \(= \,{[{T^2}]^2}[{T^{ - 1}}] = [{T^3}]\) .