The neutral part of the atom resides in the __________.

The nucleus is where the neutral part of the atom resides because it contains neutrons, which are subatomic particles that carry no electric charge. The nucleus is the central core of an atom, made up of protons and neutrons. While protons are positively charged, neutrons have no charge, contributing to the overall neutrality of an atom when paired with an equal number of protons.

In contrast, the electron cloud surrounds the nucleus and contains electrons, which are negatively charged particles. Options referring to the cytoplasm and proton layer do not pertain to atomic structure, as cytoplasm is related to cell biology, and there is no specific "proton layer" in atomic theory. Hence, the nucleus is indeed the correct answer.