* Element: Made up of only one type of atom (e.g., gold, oxygen).

* Molecule: Two or more atoms bonded together, but they can be the same type of atom (e.g., oxygen gas - O2).

* Compound: Made up of two or more different types of atoms chemically bonded together (e.g., water - H2O, table salt - NaCl).

* Matter: Anything that has mass and takes up space. This is a broad category that includes all of the above.

Therefore, a compound is the only option that *must* be made of at least two different types of atoms.