The control center and director of cell activities is the

endoplasmic reticulum
nucleus
mitochondria
lysosomes

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.

the answer is d p: cell, q: organ, r: organ system, s: tissue