The correct answer is: B. it reduces the surface tension of solution.
Soap is a surfactant, which means it lowers the surface tension of water. This allows the water to more easily penetrate the fabric and remove dirt and oil.
Option A is incorrect because soap does not act like a catalyst. A catalyst is a substance that speeds up a chemical reaction without being consumed by the reaction. Soap does not speed up the chemical reaction of cleaning, but it does make it more effective.
Option C is incorrect because soap does not give strength to solution. Soap is a surfactant, which means it lowers the surface tension of water. This does not make the solution stronger, but it does make it more effective at cleaning.
Option D is incorrect because soap does not absorb the dirt. Soap helps to loosen dirt and oil from the fabric so that it can be rinsed away with water.