GKFix MCQ Question

What is the expression for torque on a system of particles about the origin?

• A. τ = Σ (rᵢ · Fᵢ)
• B. τ = Σ (Fᵢ × rᵢ)
• C. τ = Σ (rᵢ + Fᵢ)
• D. τ = Σ (rᵢ × Fᵢ)