B, graphite is used to make electrodes, using the excellent conductivity of graphite, correct;
C, carbon dioxide generally can't burn, also does not support combustion. It is correct that carbon dioxide is used to put out fires, using both its physical properties and its chemical properties;
D, neon lights in a slender glass tube, filled with thin gas, both ends of the tube are equipped with electrodes, which produce colored light when discharging, which is correct;
So choose a.