Question

the smallest particle of an element made of electrons, protons, and neutrons
thermal energy
gas
inert
atom

Explanation:

An atom is defined as the smallest particle of an element that retains its chemical properties, and it consists of electrons, protons, and neutrons. Thermal energy is related to heat, gas is a state of matter, and inert refers to non - reactive substances, so they don't match the description.

Answer:

D. Atom (assuming the options are labeled as A. Thermal Energy, B. Gas, C. Inert, D. Atom; if the last option is "Atom" without a letter, then "Atom")