Elements are pure substances made up of atoms molecules compounds neutrons

atoms

Explanation:

An atom is smallest unit of a matter or substance.It consist of three subatomic particles : electrons, protons, neutrons. It may or may not have independent existence.

A molecule of element is formed by combination of atoms of similar elements.

A molecule of compound is formed by combination of atoms from different elements.Example:

Element is a pure substance which is composed of atoms of similar elements. Example:

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.  Example:

i think it's c. i'm not sure but i think so.

i think it is true since you can test the answer and can use observations to complete it.