Which of the following describes the major function of serous membranes?

A) Each consists of a mesothelium supported by dense connective tissue.
B) They line body cavities that communicate with the exterior.
C) They are loosely attached to the body wall and to the organs they cover.
D) Their parietal and visceral portions never touch.
E) Tiny amounts of transudate formed on the surfaces of the membrane reduce friction.