Which of the following are simple forms of lipids?

The correct answer focuses on the characteristics of simple forms of lipids, which include fats, oils, and waxes. These substances are primarily composed of fatty acids and glycerol, which are essential components of lipid structure.

Fats and oils are classified as triglycerides, where three fatty acid molecules are esterified to one glycerol molecule. They're known for their roles in energy storage, insulation, and as a source of essential fatty acids. Waxes, on the other hand, are esters of long-chain fatty acids with long-chain alcohols, providing protective coatings for plants and animals as well as contributing to waterproofing.

This choice accurately reflects the definition of simple lipids because each of these components is primarily made up of fatty acids. The other options include substances that either do not fall under the lipid category or are more complex, like proteins and sugars, which are not classified as lipids. Thus, this choice appropriately identifies simple forms of lipids based on their structure and biological function.