Question

which of the following is an example of newtons third law?
a swimmer pushes water backward and moves forward
a car accelerates when the gas pedal is pressed
a ball rolling on the ground slows down due to friction
a book stays at rest on a table

Explanation:

Newton's Third Law states that for every action, there is an equal and opposite reaction. When a swimmer pushes water backward (action), the water pushes the swimmer forward (reaction). A car accelerating when the gas pedal is pressed relates to Newton's Second Law ($F = ma$). A ball slowing down due to friction is also related to forces (friction) acting on an object (Newton's Second Law conceptually as $F_{net}=ma$, here $F_{friction}$ causes deceleration). A book staying at rest on a table is due to the balance of forces (normal force and gravitational force, which is more related to Newton's First Law - an object at rest stays at rest if net force is zero).

Answer:

A. A swimmer pushes water backward and moves forward