Compare the two kinds of telescopes property by property.
Wavelength: optical telescopes use visible light with wavelength near 500 nanometres. Radio telescopes use radio waves with wavelength from centimetres to metres, thousands of times longer.
Scattering by clouds: scattering of waves by small particles becomes weaker as wavelength increases. Since the radio wavelength is huge compared to cloud droplets, radio waves pass straight through clouds while visible light gets blocked or scattered.
Effect of sunlight: an optical telescope cannot be used in daytime because scattered sunlight floods the instrument. A radio telescope is not blinded this way, so it can operate continuously, day and night.
Faint distant sources: many galaxies and nebulae radiate strongly in the radio band even when they are too dim or too dust obscured to see in visible light, so radio telescopes reveal objects optical telescopes cannot.
Every one of these points favours the radio telescope over the optical one, which is exactly why the answer combines them all under option D.