Hadrons consist of quarks bound by the strong force

Steps:

• Define hadron as a composite particle held by the strong nuclear force.
• Identify fundamental particles as quarks and leptons, which are not composite.
• Recall that quarks combine via gluons to form hadrons like protons and mesons.
• Match quarks to the choice that fits as the building blocks.

Why D is correct:

• By definition, hadrons are subatomic particles composed of quarks interacting through the strong force, as per quantum chromodynamics.

Why the others are wrong:

• A. Leptons: Fundamental particles that do not feel the strong force and thus cannot form hadrons.
• B. Nucleons: Composite hadrons made of quarks, not fundamental particles.
• C. Photons: Massless bosons that mediate electromagnetism, not constituents of matter particles like hadrons.

Final answer: D