Which frequency band has the smallest first Fresnel zone?

The Fresnel zone is an elliptical region of space between and around a transmitting and receiving antenna. For a clear line-of-sight path, this zone must be mostly free of obstacles to prevent signal attenuation from out-of-phase reflections. The physical size of the Fresnel zone is directly proportional to the wavelength of the transmitted signal. Because higher frequencies have shorter wavelengths, their signals require a narrower clear path. Looking at the provided options, 5.8 GHz is the highest frequency. Therefore, it has the shortest wavelength and the smallest first Fresnel zone compared to 900 MHz, 2.4 GHz, or 3.4 GHz.