Which of the following is considered the fundamental building block of all matter?

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

Answer: (B)

Verified step by step guidance

1. Understand the question is asking for the fundamental building block of all matter, which means the smallest unit that retains the properties of an element.
2. Recall that a molecule is made up of two or more atoms bonded together, so it is not the most fundamental unit.
3. Recognize that electrons and protons are subatomic particles, components of atoms, but individually they do not represent matter as a whole.
4. Identify that an atom is the smallest unit of an element that maintains its chemical properties and is considered the fundamental building block of matter.
5. Conclude that among the options given, the atom is the correct answer because it forms the basis of all matter.