Particle compositions in the Standard Model

Steps:

• Recall that fundamental particles include leptons and quarks, while hadrons are composites.
• Check A: Antineutrinos are elementary leptons, confirming it's fundamental.
• Check B: Electrons are elementary leptons, not quark composites.
• Check C and D: Neutrinos are leptons; neutrons are baryons with three quarks (udd).

Why B is correct:

• Electrons are fundamental leptons, indivisible and not formed from quarks or antiquarks per the Standard Model.

Why the others are wrong:

• A: Antineutrinos are fundamental particles as neutral leptons.
• C: Neutrinos are indeed leptons, a category of fundamental fermions.
• D: Neutrons consist of three quarks: one up and two down.

Final answer: B