Correct answer: Soap: sodium salt of oleic acid
Soaps are sodium/potassium salts of long-chain fatty acids; oleic acid is such a fatty acid, so sodium oleate is a soap. Sodium lauryl sulphate is an anionic synthetic detergent, sodium stearate is a soap (not a fat), and a glyceryl ester of stearic acid is a fat (not a detergent).