Answer: Option (a) is the correct answer.
Explanation:
When gases, liquids, or solids are in contact with a moving object then friction occurs due to the movement of objects in opposite directions.
During this opposite movement, bonds between the molecules of respective objects break and again their is formation of new bonds.
This breaking or making of bonds results in the formation of energy in the form of heat.
Thus, we can conclude that when gases, liquids, or solids are in contact with a moving object, the flow of heat occurs due to frictional forces.
