What are the extremely small particles that form all matter, including humans?

The correct choice is atoms, as they are the fundamental building blocks of all matter, including humans. An atom consists of a nucleus, which contains protons and neutrons, surrounded by electrons that orbit the nucleus. Atoms combine in various ways to form molecules, which are groups of two or more atoms bonded together.

In the context of human makeup, our bodies are composed of countless atoms that come together to form the various substances we need for life, such as proteins, lipids, carbohydrates, and nucleic acids. Each of these macromolecules is made up of different arrangements and combinations of atoms. Therefore, understanding atoms is crucial because they are the most elemental units of matter that contribute to the structure and function of everything in the universe, including living organisms.