As soon as possible pls clear my doubt i think it is b

Correct, it is b

Explanation:

The explanation is basically in the question. It allows you to breath more while  breaking down food.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

i dont know it at allnow im just getting points at this pint