Final answer:
The nucleus of an atom is very small and dense, located centrally, and contains nearly all the mass of the atom despite its tiny size relative to the entire atom.
Step-by-step explanation:
The correct answer is d, the nucleus of an atom is very small and dense and is located in the center of the atom. Rutherford's atomic model, often referred to as the nuclear model of the atom, helped to determine that the protons and neutrons are located within the nucleus, which occupies a central position in the atom. The electrons, which are much lighter, are distributed around the nucleus and occupy most of the volume of the atom.
Despite containing nearly all the mass of the atom, the nucleus is remarkably small compared to the entire atom. For example, if an atom were scaled up to the size of a football stadium, the nucleus would be about the size of a marble. This highlights the vast difference in scale between the nucleus and the rest of the atom, with the diameter of the nucleus being roughly 100,000 times smaller than the diameter of the atom itself.