Why did Thomson observe two glowing dots when he put neon gas into a cathode-ray tube?

(A) The neon contained impurities
(B) The neon was made up of two different isotopes whose atoms had different
chemical properties.
(C) The neon was made up of two different isotopes whose atoms had different
masses.
(D) The neon was made up of two different isotopes whose atoms had different
charges.