The alpha particle scattering experiment, often called Rutherford`s experiment, focused on the passage of alpha particles (helium nuclei) through a very thin gold foil.
Option 1 and 2 suggest the presence of electrons and protons respectively, which are components of an atom. However, the gold foil experiment revealed not just their presence, but about the very structure of the atom itself.
Option 4 suggests that the experiment reveals the presence of isotopes of gold, but this is not correct. The alpha scattering experiment does not give insights about isotopes.
Option 3 is correct. The scattering pattern of the alpha particles suggested that atoms have a small, dense, positively charged nucleus at the center, because only a concentrated positive charge could repel the positively charged alpha particles in different directions. This inference l in option 3 fundamentally changed the understanding of atomic structure.