which of the following factors affect friction? select all that apply a the smoothness of the surfaces that…

which of the following factors affect friction? select all that apply a the smoothness of the surfaces that are touching. b the amount of force that is pressing them together. c the use of lubricants between the two surfaces. d all of the above.
Answer
Brief Explanations:
La fricción depende de la rugosidad (opuesto a la suavidad) de las superficies en contacto, la fuerza normal (que es la fuerza que las aprieta) y la presencia de lubricantes que reducen la fricción.
Answer:
d. All of the above.