What is the main muscle of breathing and what are its characteristics?

I - The diaphragm is a muscle-tendon septum that separates the thoracic and abdominal cavities.
II - The diaphragm is composed of a muscular portion and an aponeurotic portion.
III - The diaphragm has three main orifices that allow important structures to pass through it.
IV - The diaphragm is not involved in the process of urination, defecation, and childbirth.
a) Only I and II are correct.
b) Only II and III are correct.
c) Only I, II, and III are correct.
d) Only III and IV are correct.
e) All statements are correct.