Tristearin is a triglyceride, which is an ester of glycerol and three fatty acid molecules. Alkaline hydrolysis of fats and oils, a process called saponification, yields soap (the salt of the fatty acid) and glycerol. Glycerol, also known as propane-1,2,3-triol, is an alkanol with three hydroxyl (-OH) groups in its structure, making it a trihydric alkanol.

A. dihydric alkanol is incorrect because a dihydric alkanol (e.g., ethane-1,2-diol or glycol) has only two hydroxyl groups, while glycerol produced from the reaction has three.

B. tertiary alkanol and C. secondary alkanol are incorrect because they refer to the position and number of hydrogen atoms attached to the carbon atom bearing the hydroxyl group in monohydric alcohols. The product, glycerol, is a trihydric alkanol.