Concept:Soap cleans by lowering the surface tension of water, allowing water to spread and wet greasy surfaces more easily.
Explanation:Water normally has high surface tension, which makes it form droplets and prevents it from spreading evenly over oily or dirty surfaces.
Soap molecules have one end that attracts water and another end that attracts grease and dirt.
When soap is added, its molecules position themselves between the water molecules at the surface.
This weakens the pulling forces between the water molecules, so the surface tension is reduced.
With lower surface tension, water can spread out, surround dirt particles, and wash them away.
Therefore, the cleaning action of soap is based on the principle of surface tension.
Answer:D. surface tension