31. Cathode-ray tubes experiments conducted by J. J. Thomson evidenced the presence of(A)Protons(B)Electrons(C)X-ray(D)Photons

39. Chlorine exists naturally as a mixture of chlorine-35 and chlorine-37 isotopes. An atom of chlorine-35 contains(A)17 protons, 18 neutrons, 17 electrons.(B)16 protons and 17 electrons, only.(C)18 protons, 18 electrons, and 17 neutrons.(D)17 protons, 35 neutrons, and 17 electrons.