You are approached by a neighboring group of human survivors and they are wanting to know what you are shooting at the alien craft so you can see them at night. Choose the right explanation for this effect.

a Chemicals in the paint absorb light energy in a process called phosphorescence, radioactive elements keep the glow going.
b Key element is sulfur and the sulfur creates light after being heated in a process called sulfunescense
c Chlorine is the reason why the alien vessels glow.
d Calcium make the light when the craft comes into contact with water