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) Both conditions a and b above must be fulfilled.
D) Wrong! Visual light wavelengths are used because they are blocked by dust between the stars.