Rutherford’s $\propto$-particle scattering experiment led to the discovery of:

Most of the particles released by a radioactive source in Rutherford's experiment returned to the source after passing through a gold foil. Only the presence of a positively charged heavy particle (nucleus) in the centre makes this conceivable. So, this experiment resulted in the identification of the atomic nucleus.

Rutherford, a prominent physicist, provides an explanation for particle scattering. According to Rutherford's experiment, the alpha particles that are present in every atom are spread widely. In this experiment, the idea of coulombs interaction between the atoms is used to explain the dispersion of particles. He demonstrates that the nucleus, the region at the heart of the atom where very dense particles are present, exists. Rutherford's team of researchers is therefore credited with discovering the nucleus in 1911 as a result of the scattering experiment.

Protons and neutrons are the concentrated charged particles found in the nucleus. Thus, Rutherford's scattering experiment contributed to the identification of the atom's nucleus.

Hence, the correct option is (D).