Final answer:
The substances classified as lipids are oils and waxes. Cholesterol is categorized as a steroid, a sub-type of lipids.
Step-by-step explanation:
The classified lipids among the options provided are oils and waxes. Lipids are macromolecules that are hydrophobic and include various types such as fats and oils, waxes, phospholipids, and steroids. Disaccharides and cellulose are carbohydrates; essential amino acids are proteins; mRNA and DNA are nucleic acids.
Cholesterol is specifically classified as a steroid, which is a type of lipid known for its four fused carbon rings structure. Cholesterol plays a critical role in cell membrane fluidity and is a precursor to steroid hormones. Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types of lipids include fats and oils, waxes, phospholipids, and steroids. From the given options, oils and waxes (d) are classified as lipids.