Carla demonstrates Newton's First Law of Motion by slowly pushing a book across a table. The book moves at a constant rate of speed so long as she is pushing it. Which of the following is NOT true? (1 point)
• The forces acting on the book are all balanced.
• Her push balances the force of friction.
• The upward force exerted by the table balances the book's weight.
• There is an unbalanced force on the book, acting in the direction of motion.