One difference between mixtures and pure substances is that a) mixtures can be physically separated. b) mixtures are made of one type of atom. c) pure substances have no chemical bonds. d) pure substances can be physically separated.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.

i think it's c. if you look search electronic symbol on google and then click on wiki it shows you a