the role of the lipids is Lipids perform three primary biological functions within the body: they serve as structural components of cell membranes, function as energy storehouses, and function as important signaling molecules. The three main types of lipids are triacylglycerols (also called triglycerides), phospholipids, and sterols. which by this information that i found online helped me get it right hope this helps you understand.
External stimulus. The rain is something out of your control while you're waiting. Rain is not something you are doing nor is it a response to you waiting for the bus.
