Question 5
Where do frictional forces act?
The right answer is the one marked above.
Along the surfaces of the two bodies that are in contact. No contact means no friction — it is not a force that reaches across a distance the way gravity does.
The weight of an object can be treated as acting at its centre, which is probably why that option looks familiar. Friction is different: it belongs to the surfaces, not to the body as a whole.