Which of the following is a soap?

Fatty acids are molecules made up of long chains of lipid-carboxylic acid that are found in fats and oils as well as cell membranes as phospholipids and glycolipids. Soaps are salts of fatty acids. Four saturated fatty acids, myristic, lauric, palmitic, and stearic, and four unsaturated fatty acids, ricinoleic, oleic, linoleic, and linolenic, make up the eight fatty acids that makeup soap molecules. A sodium or potassium salt of a fatty acid or soap is produced during the saponification of each fatty acid. Since fatty acids have long chains of carbon atoms or at least 10 carbons, soaps are fatty acids.

Soaps are sodium or potassium salt of fatty acids. Fatty acids are esters of glycerol. Since glycerol contains three carbon atoms a fatty acid or its salt must contain a minimum of four carbon atoms. Soaps are sodium salt of long chain fatty acids. In the given options two long chain sodium salts are present. In these, sulfate salts are components of detergents and can be excluded. Therefore the correct answer is $C_{17}{H}_{35}COONa$.

Hence, option B is correct.