How is delta-v estimated for a two-stage rocket when nozzle expansion losses are considered?

How is delta-v estimated for a two-stage rocket when nozzle expansion losses are considered?

• A. Use the Tsiolkovsky rocket equation for each stage, summing the delta-v while accounting for propellant masses and effective exhaust velocities
• B. Use aerodynamic drag to reduce velocity, then sum
• C. Delta-v is independent of propellant mass
• D. Add delta-vs of stages simply by multiplying exhaust velocity by mass ratio

Answer: (B)