Question

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Answer 1

Friction resists motion.
Friction is a contact force.
Friction is caused by microscopic bumps and ridges on surfaces. 

They all correct, just took the quiz. 

Answer 2

Answers:

3 Friction is a contact force.  

4 Friction is caused by microscopic bumps and ridges on surfaces.

Explanation:

Friction is a force that opposes the motion of an object. For example, when you are sliding a box along a surface, there is a friction force that resists the motion.

The friction force is caused by the contact between the molecules of the external surfaces of the object and the molecules of the surface where the object is sliding over. Therefore, it is a contact force (statement 3) and also it is caused by the bumps and ridges on the surfaces (statement 4): in fact, if the surfaces were perfecly smooth, in theory there would be no friction (but this is impossible in reality).