explain why a seesaw is closest in arrangement to a first class lever.

Answer:

A seesaw has the fulcrum (pivot - point) in the middle, with the effort (the force applied by a person sitting on one end) and the load (the force of the person on the other end) on either side of the fulcrum. In a first - class lever, the fulcrum is located between the effort and the load. So, a seesaw's arrangement matches the basic structure of a first - class lever.

Brief Explanations:

First - class lever has fulcrum between effort and load, which is the case for a seesaw.