Explanation

(c) In ground wave propagation, radio waves travel along the surface of the earth (following the curvature of earth). Ground wave propagation can be sustained only at low frequencies $(\sim\ 500\ kHz\ to\ 1500\ kHz)$ or for radio broadcast at long wavelengths.
Satellite communication is useful for the frequencies above 30 MHz which takes place through tropospheric space. The phenomenon involved in the sky wave propagation is total internal reflection.