If the airplane returns to the departure airport immediately after takeoff, how is the cabin altitude controlled?

When an airplane returns to the departure airport immediately after takeoff, the cabin altitude system is designed to automatically adjust back to the elevation of the takeoff location. This is due to the aircraft's automated systems which continuously monitor and control the cabin pressure based on altitude changes. When the aircraft descends back to the original elevation, the cabin pressure situation is likewise modified to ensure passenger safety and comfort, preventing abrupt pressure changes that could occur if the system did not auto-adjust.

The other options involve processes that would not typically be necessary in this situation. Manually setting the departure elevation or controlling the cabin altitude manually is not standard practice during such an immediate return, as the systems are engineered for automatic adjustment to optimize safety and efficiency. The requirement for depressurization and manual control does not apply under normal operational protocols when simply returning to the departure point shortly after takeoff.