Step 1: Concept
Lipids are stored in organisms to serve as long-term energy reserves.
Step 2: Meaning
Storage lipids are neutral fats composed of three fatty acids esterified to a glycerol backbone.
Step 3: Analysis
Triacylglycerols (also called triglycerides) are highly concentrated energy stores because they are reduced and anhydrous. Sphingolipids, glycolipids, and cholesterol are primarily structural components of membranes.
Step 4: Conclusion
Triacylglycerol is the primary storage lipid.
Final Answer: (D)