14. Which of the following masses is the smallest? (Hint: A neutron can decay into a proton, an electron, and an antineutrino.)
(A) The mass of a Helium-4 atom (a stable atom consisting of two protons, two neutrons, and two electrons)
(B) The total mass of an alpha particle (a helium ion consisting of two protons and two neutrons) and two electrons
(C) The total mass of two protons, two neutrons, and two electrons
(D) The total mass of one proton, three neutrons, and one electron
(E) All the above are the same