Quark content in tritium nucleus

Steps:

• Hydrogen-3 (tritium) nucleus contains 1 proton and 2 neutrons.
• A proton consists of 2 up quarks and 1 down quark.
• A neutron consists of 1 up quark and 2 down quarks.
• Total down quarks: 1 (proton) + 2 × 2 (neutrons) = 5.

Why D is correct:

• By the standard quark model, the tritium nucleus (1 proton + 2 neutrons) has exactly 5 down quarks.

Why the others are wrong:

• A. 2: Counts only proton and one neutron's downs, ignoring the second neutron.
• B. 3: Matches total baryon number but ignores quark breakdown.
• C. 4: Counts downs from neutrons only, omitting the proton's down quark.

Final answer: D