Answer:
D. Quarks pair with other quarks to form protons and neutrons.
Explanation:
Quarks are one of the types of fundamental particles: in particular, they are the particles that form hadrons (consisting of 3 quarks) and mesons (consisting of 2 quarks).
Protons and neutrons are hadrons, so they consist of 3 quarks each: therefore, this statement:
D. Quarks pair with other quarks to form protons and neutrons.
is the correct one.
The other statements are wrong because:
A --> protons and neutrons do not contain leptons (leptons are other fundamental particles, such as the electron and the muon)
B --> bosons at the mediators of the fundamental forces, and they do not consist of quarks. Photon is one of the bosons.
C --> protons and neutrons do not contain photons
E --> protons do not contain electrons