Which of the following terms refers to the basic building blocks of matter?

The term that refers to the basic building blocks of matter is "atom." Atoms are the smallest units of an element and consist of a nucleus surrounded by electrons. They combine to form molecules and compounds, which are larger structures made up of two or more atoms chemically bonded together. Understanding the concept of atoms is fundamental to various fields, including chemistry and physics, as they serve as the foundational units from which all substances are composed. Molecules, while composed of atoms, are not the basic building blocks themselves but rather aggregates of two or more atoms. Electrons are subatomic particles within atoms, and compounds are substances formed when two or more different types of atoms bond together. Thus, atoms are indeed the true fundamental units of matter.