The presence of protons and neutrons at the center of the atom was suggested by:

• A
  Protons by $J. Chadwick$ and neutrons by $E. Goldstein$
• B
  Protons by $E. Goldstein$ and neutrons by $J. Chadwick$
• C
  Protons by $E. Goldstein$ and neutrons by $J.J. Thomson$
• D
  Protons by $J. Chadwick$ and neutrons by $J.J. Thomson$