What distinguishes first class levers from both second and third class levers?
a. the fulcrum is between the load and effort.
b. there is a fulcrum on both sides of the load.
c. greater effort is required to move the load.
d. the first class lever is not found in the human body

In the first class lever the fulcrum is located between the effort and the resistance.In second class lever The second class of lever has the fulcrum at one end, the effort applied at the other end, and the resistance somewhere between those points. [ The third class of levers has the fulcrum at one end of the lever, and the weight or resistance to be overcome is at the other end, with the effort applied at some point between. ]