The plane had taken off. Paul realized he was on the wrong flight

A. Hardly had Paul realized he was on the wrong flight when the plane took off.

B. It was not until the plane had taken off, did Paul realize he was on the wrong flight.

C. Not until the plane had taken off did Paul realize he was on the wrong flight.

D. No sooner had the plane taken off than Paul had realized he was on the wrong flight.