Current Searches for Extraterrestrial Intelligence Use Radio Telescopes at Wavelengths

Current searches for extraterrestrial intelligence use radio telescopes at wavelengths

A) which must be shorter than the local wavelengths emitted by Earth's atmosphere.
B) which must be longer than the radio wavelength 'noise' naturally emitted by our galaxy.
C) which must be longer than the local wavelengths emitted by Earth's atmosphere and which must be shorter than the radio wavelength 'noise' naturally emitted by our galaxy.
D) Wrong! Visual light wavelengths are used because radio waves are blocked by dust between the stars.