Final answer:
Waxes are esters formed from a long-chain alcohol and a high molecular weight fatty acid, not from glycerol, phosphate diester, or triacylglycerol. The correct answer is (b) Fatty acid.
Step-by-step explanation:
Waxes are esters formed from a long-chain alcohol and a high molecular weight fatty acid. Choices such as glycerol, phosphate diester, and triacylglycerol are incorrect as they refer to other types of lipid molecules. For example, triacylglycerol, also known as a triglyceride, consists of glycerol and three fatty acids. However, in waxes, the structure is different: the ester is made from a long-chain fatty acid and a long-chain alcohol, which results in a long carbon chain with typically 14 to 30 carbons per chain and a different set of properties compared to triglycerides. Examples of waxes include beeswax, which is made from esters of oleic acid and oleyl alcohol (both containing 18 carbons), and myricyl palmitate found in beeswax, created by the esterification of palmitic acid and myricyl alcohol. These waxes are characterized by being soft solids with low melting points and are insoluble in water. Therefore, the correct answer to the student's question is (b) Fatty acid.