The correct answer is B. sodium salt of benzene sulphonic acid.
Synthetic detergents are made from petroleum-based chemicals. They are long-chain molecules with a polar end and a nonpolar end. The polar end is attracted to water, while the nonpolar end is attracted to oil and grease. This makes synthetic detergents effective at cleaning both water-based and oil-based dirt.
Sodium stearate, sodium palmitate, and sodium salt of benzene carboxylic acid are all soaps. Soaps are made from natural fats and oils. They are also long-chain molecules with a polar end and a nonpolar end. However, the polar end of a soap molecule is a carboxylate group, while the polar end of a synthetic detergent molecule is a sulfonate group. Carboxylate groups are more water-soluble than sulfonate groups, which is why soaps are less effective at cleaning oil-based dirt than synthetic detergents.
In addition, soaps can form scum when they are used in hard water. This is because the calcium and magnesium ions in hard water react with the carboxylate groups in soap molecules to form insoluble salts. Synthetic detergents do not form scum in hard water because they do not have carboxylate groups.
For these reasons, synthetic detergents are more effective and versatile than soaps. They are used in a wide variety of products, including laundry detergent, dishwashing detergent, and shampoo.