Which of these equations represent 1-D steady state diffusion?

• A. div(Γ grad Φ)+S=0
• B. \(\frac{d}{dx}(\Gamma\frac{d\phi}{dx})+S=0\)
• C. \(\frac{d\phi}{dt}+\frac{d}{dx}(\Gamma\frac{d\phi}{dx})+S=0\)
• D. \(\frac{d\phi}{dt}+div(\Gamma grad\phi)+S=0\)