Which of Newton's laws of motion is demonstrated by a hammer pounding a nail into a board

The answer is Newton's third law.

In pounding a nail into the board using the hammer, third law of Motion given by Newton is followed or demonstrated.

Explanation:

''For every action, there is an equal and opposite reaction'' is the third ''Law of Motion'' that is given by Newton. When a hammer hits the nail into the board, which exerts the on the nail, in reaction to which nail exerts the same amount of force but in opposite direction force. With this action the pair of forces and nail is pounded into the board.