Answer the following question given this paragraph: 

Rougher surfaces have more friction between them than smoother surfaces. That’s why we put sand on icy sidewalks and roads. The blades of skates are much smoother than the soles of shoes. That’s why you can’t slide as far across ice with shoes as you can with skates (see Figure below ). The rougher surface of shoes causes more friction and slows you down. Heavier objects also have more friction because they press together with greater force. Did you ever try to push boxes or furniture across the floor? It’s harder to overcome friction between heavier objects and the floor than it is between lighter objects and the floor.


Q: What force is greater on rougher surfaces than smooth surfaces?

 Choices:

- tension

- acceleration

- gravity

- friction

A:
friction
