Which of the following particles have a neutral charge? a) atom b) proton c) ion d) neutron

Consider all the listed elementary charges:
Atom – consists of a nucleus (neutrons and protons) and electrons. Under normal conditions, an atom has no charge, since electrons and protons cancel each other out. Therefore, he is neutral.
Proton – has a positive charge.
Ion – depending on the conditions, has either a positive or negative charge. There are no neutral ions.
Neutron – has no charge. Therefore, he is neutral.
That is, the correct answers are: a) an atom and d) a neutron.