c
Comparing the given equation with standard equation of standing \(\frac{2 \pi \mathrm{n}}{\lambda}=\omega \& \frac{2 \pi}{\lambda}=\mathrm{k}\)

\({\left[\frac{\mathrm{n}}{\lambda}\right]=[\omega]=\mathrm{T}^{-1}}\)

\({[\mathrm{nt}]=[\lambda]=\mathrm{L}}\)

\({[\mathrm{n}]=[\lambda \omega]=\mathrm{LT}^{-1}}\)

\({[\mathrm{x}]=[\lambda]=\mathrm{L}}\)

Hence option \((3)\)