Final answer:
Lipids are the biomolecules found in fats, oils, and waxes, serving as a long-term energy source while also fulfilling critical roles in cellular structure and the absorption of fat-soluble vitamins.
Step-by-step explanation:
The biomolecule found in fats, oils, and waxes that serves as a source of long-term energy is C) Lipid. Lipids are a class of macromolecules known for being nonpolar and hydrophobic, which includes fats, oils, waxes, phospholipids, and steroids. These molecules are particularly efficient for long-term energy storage, housing more than twice the calorific value of carbohydrates—approximately 9 kcal/g for lipids compared to only 4 kcal/g for carbs. Hence, lipids are vital not only as an energy reserve but also play key roles in cellular membrane structure, organ insulation, and shock absorption, as well as being essential for absorbing fat-soluble vitamins such as A, D, E, and K.