Answer : The correct option is, protons and neutrons.
Explanation :
As we know that an atom is the smallest unit of a matter that consist of three subatomic particles. The subatomic particles are electrons, protons and neutrons.
The protons that are positively charged and the neutrons that are neutral that means no charge are located inside the nucleus or center of the nucleus of an atom. In the nucleus, the mass of the an atom is concentrated and the electrons that are negatively charged located around the nucleus.
Hence, the particles make up the nucleus of an atom are protons and neutrons.