Option 1 states that detergents reduce the surface tension between water and oil. Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. In the case of water and oil, they do not easily mix because water molecules are attracted to each other more strongly than they are attracted to oil molecules. This results in water forming droplets on top of the oil.

Detergents contain molecules that have a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail. When detergent is added to water, the hydrophilic heads are attracted to the water molecules, while the hydrophobic tails are repelled by them.

The hydrophobic tails of the detergent molecules are attracted to the grease and oil stains on the clothes. As the detergent molecules surround the oil molecules, they form structures called micelles. The hydrophilic heads point towards the water, while the hydrophobic tails trap the grease and oil stains inside the micelles.

By reducing the surface tension between water and oil, detergents essentially help break down the grease and oil stains from the clothes, allowing them to mix with the water and be rinsed away during the washing process. Therefore, option 1 is correct.