All the materials by schools seem to focus on the Bernoulli theory as the main contributor of lift so I'd reckon most people would choose D?
Wouldn't the Newton 3rd law theory be pretty practical and acceptable when it comes to flaps? The notes I have with me explain that flaps only serve to increase the mean camber of the wing but how does this effectively increaase the lift by so much at lower speeds? The curvature of the trailing edge does seem to provide a force on the airflow and change its direction downwards which in return provide lift according to Newton's 3rd law?