Answer:
B. electron
Explanation:
A sub- atomic particle is any of self-contained units of matter or energy that are the fundamental constituents of matter. They include: electrons, protons and neutrons.
A compound is a substance formed by the chemical combination of elements in fixed proportions.
An isotope is any of the two or more atoms that have the same atomic number but different mass numbers due to the difference in neutron numbers.
A neuron is a cell, usually consisting of a cell body, axon, and dendrites, that transmits nerve impulses and is the basic functional unit of the nervous system.
