Which description matches a quark?

• A. A neutral particle in the nucleus.
• B. A particle larger than an atom.
• C. Charged particle that is smaller than a proton.
• D. A force carrier in atoms.

Answer: (C)

Quarks are the tiny building blocks that combine to form protons and neutrons inside the nucleus. They are much smaller than a proton and carry fractional electric charge, either +2/3 or -1/3. Because of that, describing a quark as a charged particle that is smaller than a proton is accurate and precise. The other descriptions don’t fit: a neutral particle in the nucleus would describe a neutron, which is made of quarks but is not a single quark itself; quarks are not larger than an atom; and a force carrier in atoms is something like a photon or a gluon, not a quark.