What distinguishes the three different classes of levers found in the human body? a. where they are located in the body b. how useful they are for performing work c. where the components of the lever are located d. how many moving parts the lever has

The right option is C. where the components of the lever are located.

A lever is a rigid piece (a length of bone) that has the ability to turn about a pivot (a joint). Levers are formed by the combined actions of muscles and bones. They can be used to intensify movement such as when kicking a ball and they are capable of providing a movement or a strength benefits but not the two together. Levers are mainly grouped as first class, second class, or third class and they are distinguished by the way the joint and muscles attached to the bone are arranged and found in the human body.

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.

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