Quark charges must sum to zero for a neutral baryon

Steps:

• Recall quark charges: up (+2/3 e), down (-1/3 e), strange (-1/3 e).
• Compute total charge for each composition by adding individual charges.
• Identify the option where the sum equals zero.
• Confirm it forms a baryon (three quarks).

Why B is correct:

• Up (+2/3), down (-1/3), and strange (-1/3) sum to zero per the additive charge rule for composite particles.

Why the others are wrong:

• A: Two downs and strange yield -1/3 -1/3 -1/3 = -1 charge.
• C: Two ups and down yield +2/3 +2/3 -1/3 = +1 charge.
• D: Two ups and strange yield +2/3 +2/3 -1/3 = +1 charge.

Final answer: B