Which of these formulae is used for the corrector step of the two-level predictor-corrector method?

• A. Φn+1=Φn+\(\frac{1}{3}\) [2f(tn,Φn )+f(tn+1,Φn+1*)]Δt
• B. Φn+1=Φn+\(\frac{1}{2}\) [2f(tn,Φn )+f(tn+1,Φn+1*)]Δt
• C. Φn+1=Φn+\(\frac{1}{3}\) [f(tn,Φn )+2f(tn+1,Φn+1*)]Δt
• D. Φn+1=Φn+\(\frac{1}{2}\) [f(tn,Φn )+f(tn+1,Φn+1*)]Δt