An alpha particle is like a Helium atom. And Helium has an atomic number of 2 and mass number or 4.
Mass Number =4,
Atomic Number = 2, for a Neutral Atom, Atomic Number = Number of Proton = 2
Mass Number = Proton + Neutron.
4 = 2 + Neutron
Neutron = 4 -2 = 2
Hence alpha particle has 2 Protons and 2 Neutrons. Option C.