According to the electron theory, atoms are composed of which of the following?

The correct response highlights the foundational structure of atoms in accordance with the electron theory, which states that all matter is made up of atoms. Atoms are themselves composed of three primary subatomic particles: electrons, protons, and neutrons.

Electrons are negatively charged particles that orbit the nucleus of the atom, which contains protons and neutrons. Protons are positively charged, while neutrons have no charge, making them neutral. This arrangement is crucial for understanding how atoms interact with each other in chemical reactions and how they form molecules. The balance between protons and electrons determines the atom's chemical properties, while neutrons contribute to the atomic mass and stability of the nucleus.

In contrast, the other answer choices incorporate incorrect combinations of components that do not accurately reflect the makeup of an atom. For instance, the reference to "matter" and "elements" does not pertain to the standard three-part composition of atoms as established in the electron theory. Understanding this structure is key to grasping more complex concepts in both chemistry and physics, particularly in relation to chemical bonding and electron configurations.