Currently, astronomers are observing the universe across many different regions of the electromagnetic spectrum, from gamma rays to radio waves. one of the primary issues when considering communication with potential life outside our planet is how an extraterrestrial signal would be distinguished from natural radiation sources. sort the following source properties by whether they might be considered as originating from intelligence or simply be natural phenomena: 1) constant, unchanging signal2) random radio fluctuations3) sequence of pulses varying over time4) single strong visible light burst that fades away over months5) identical repetitive pulses