The equation $\mathrm{Y}={\cos }^2\left(2\mathrm{\pi nt}-\frac{2\mathrm{\pi x}}{\mathrm{\lambda }}\right)$ represent a wave with

amplitude a / 2, frequency 2 n and wavelength $\lambda$

amplitude a/2, frequency 2 n and wavelength $\lambda$/2

amplitude a, frequency n and wavelength $\lambda$

amplitude a, frequency 2 n and wavelength 2$\lambda$