Which of the following represents the steady-state diffusion equation for a homogeneous, one-speed reactor with a source term S, including the fission production term?

• A. -∇ · D ∇ φ - Σ_a φ = (ν Σ_f φ)/k_eff + S
• B. -∇ · D ∇ φ + Σ_a φ = (ν Σ_f φ)/k_eff + S
• C. ∂φ/∂t = D ∇^2 φ - Σ_a φ + S
• D. -∇ · D ∇ φ - Σ_a φ = S

Answer: (B)