What is the equivalent of (ρC ΦC)t+Δt/2 using the Crank-Nicolson scheme for finite volume approach?

• A. \(\frac{1}{2}\)(ρC ΦC)t+\(\frac{1}{2}\)(ρC ΦC)t+Δ t
• B. (ρC ΦC)t+(ρC ΦC)t+Δt
• C. (ρC ΦC)t-(ρC ΦC)t+Δt
• D. \(\frac{1}{2}\)(ρC ΦC)t–\(\frac{1}{2}\)(ρC ΦC)t+Δt