Depending on how I felt that day, I would mostly, A. Sit in the middle seat. B. Sit in the window seat or C. Inform the cabin after we had leveled out, that there was an open window seat over here.
D. would just be me trying to lay down over all of them. The dick move for sure.
having all three seats free allows you to stretch your legs sideways while sitting in the middle seat, so you never need to retract them when flight attendants or other passengers pass by