Which particle is positively charged?

The correct choice is the proton, which is a fundamental particle found in the nucleus of an atom. Protons carry a positive electric charge, which is essential in defining the atomic number of elements. This positive charge contributes to the electromagnetic interactions that hold atoms together, as protons attract negatively charged electrons, allowing for the formation of stable atoms.

In contrast, neutrons are neutral particles with no charge, electrons carry a negative charge, and photons are particles of light that are also electrically neutral. Understanding the role of protons and their positive charge is crucial in the study of atomic structure and chemistry.