Hematopoiesis refers to the formation of blood cells within the red marrow cavities of certain bones

True

Explanation:

Hematopoiesis is the production of every types of blood cells as well as blood plasma. Simply put we can define this as the way through which blood cells are manufactured by the body. This process happens in different body organs and tissues like the liver and spleen. In humans, it starts from the yolk sac, to the liver and then bone marrow.

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.

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%