Which of the following have a neutral charge?
proton
neutron
electron
plasma

The correct answer is neutron.

Explanation:

For the given options:

Option 1: Proton

This the sub-atomic particle which is present in the nucleus of an atom and carries a positive charge.

Option 2: Neutron

This the sub-atomic particle which is present in the nucleus of an atom and does not carry any charge. It is neutrally charged specie.

Option 3: Electron

This the sub-atomic particle which is present around the nucleus in the orbits of an atom and carries a negative charge.

Option 4: Plasma

This is the fourth state of matter which is hot ionized gas which may contain positive or negative charge.

Hence, the correct answer is neutron.