Which body tissues do you think contain the MOST
mitochondrla?

Muscles. Muscle cells have the most number of mitochondria in a human body. That includes the cardiac cells as well(because, the heart is also a muscular chamber, if you're not familiar).

Explanation:

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.

it's c.us forest service