Most lever systems in the human body are ________.

A) second class
B) first class
C) fourth class
D) third class

Most lever systems in the human body are third class levers, meaning the fulcrum is located at one end, the effort is applied at the other end, and the load is located between them. This is the case with many of the muscles in our body, where the fulcrum is the joint, the effort is from the muscle contraction, and the load is the weight of the limb or object being moved.