Answer: 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.
