Which of the following is considered the fundamental subunit of matter?

• A. Atom
• B. Proton
• C. Electron
• D. Molecule

Answer: (A)

Verified step by step guidance

1. Understand the question is asking for the fundamental subunit of matter, which means the smallest unit that retains the properties of an element.
2. Recall that a proton and an electron are subatomic particles, which are components of atoms but not the fundamental unit themselves.
3. Recognize that a molecule is made up of two or more atoms bonded together, so it is a larger structure than an atom.
4. Identify that an atom is the smallest unit of an element that maintains its chemical identity and properties.
5. Conclude that the atom is considered the fundamental subunit of matter because it is the basic building block of all elements.