What are prosthetics? How can they help? How are engineers trying to make them
better?

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.

wegner's theory did not explain how the continents could move

explanation: