Alkaline hydrolysis is a chemical reaction in which a compound is broken down into its constituent molecules by the addition of an alkali, such as sodium hydroxide (NaOH). This process is commonly used in the preparation of soaps.

- Lower esters are not used in the preparation of soaps, as they do not undergo alkaline hydrolysis to form soap molecules. Therefore, option 'b' is incorrect.

- Carboxylic acids are not directly used in the preparation of soaps. While carboxylic acids can react with alkali to form salts (known as carboxylate salts), they do not undergo alkaline hydrolysis to form soap molecules. Therefore, option 'a' is incorrect.

- Higher esters, on the other hand, do undergo alkaline hydrolysis to produce soap molecules. When a higher ester reacts with an alkali, such as NaOH, it is hydrolyzed into its constituent molecules: an alcohol and a carboxylate salt. The carboxylate salt acts as the soap molecule, which is responsible for the cleansing properties of soap. Therefore, option 'c' is correct.

- None of these: This option is incorrect because higher esters do undergo alkaline hydrolysis to form soap molecules. Therefore, option 'd' is incorrect.

In summary, soaps are prepared by the alkaline hydrolysis of higher esters. This process involves the reaction of higher esters with an alkali, such as NaOH, to produce soap molecules (carboxylate salts) and alcohol.