Which statement best describes the difference between strong nuclear forces and weak nuclear forces?

a. weak nuclear forces hold protons and neutrons together; strong nuclear forces hold electrons in their shells.
b. strong nuclear forces are responsible for holding electrons in bonds; weak nuclear forces are involved when the bonds break.
c. weak nuclear forces hold the atoms' nucleus together; strong nuclear forces tear them apart.
d. strong nuclear forces are responsible for holding together the nucleus of an atom; weak nuclear forces are involved when certain types of atoms break down.