Most Searches of Space for Evidence of Intelligent Life Concentrate

Most searches of space for evidence of intelligent life concentrate on radio wavelengths because:

A) Earth's atmosphere is most transparent at these wavelengths and radio signals will be more easily detected from Earth.
B) radio energy is least affected by dust and gas in the interstellar medium.
C) it is likely that extraterrestrial beings will have developed radio transmitters before developing more complex lasers or IR light transmitters.
D) radio signals can carry the greatest amount of information per unit of time, so information transfer will be most efficient at these wavelengths.