Final answer:
The fundamental building block of all matter is the atom, the smallest unit of an element that maintains the element's chemical properties. Atoms contain subatomic particles like protons, neutrons, and electrons, but it is the atom itself that is the basic building block. Option c.
Step-by-step explanation:
The particle that is considered the fundamental building block of all matter is the atom. An atom is the smallest unit of an element that retains the chemical properties of that element. Atoms join together to form molecules, which are compounds consisting of two or more atoms bonded together.
Inside every atom, there are subatomic particles, namely protons, neutrons, and electrons. Protons and neutrons reside in the nucleus at the center of the atom, while electrons orbit around the nucleus.
However, when we talk about the basic building blocks of matter, we refer to atoms, as they make up molecules and are themselves made up of protons, neutrons, and electrons.
So Option c.