Please choose the correct multiple choice answer to this respiratory question re: "why dont lungs collapse"

I am going to say "D". If it was "A" our lungs would always be collapsed. I just don't like "B". "C" could be a possibility. "E" would depend on the, actual, definition of "collapse" being used. The medical condition of a collapsed lung means that, due to whatever, the lung collapses and can not inflate on it's own, and needs to be (once the contributing factor is taken care of) reinflated.