Identify Σ^- by total charge from quark compositions

Steps:

• Quark charges: u = +2/3 e, d = -1/3 e, s = -1/3 e.
• Calculate total charge for each hadron by summing quark charges.
• Σ^- baryon has charge -e, so total must be -1.
• Match the composition yielding -1 charge with strangeness -1 (one or more s quarks).

Why D is correct:

• D (dds) sums to -1/3 -1/3 -1/3 = -1 e, matching Σ^- definition as down-down-strange baryon.

Why the others are wrong:

• A (uud): +2/3 +2/3 -1/3 = +1 e (proton-like).
• B (uds): +2/3 -1/3 -1/3 = 0 e (Σ^0 or Λ).
• C (uss): +2/3 -1/3 -1/3 = -1/3 e (not -1 e).

Final answer: D