The compound that is used for energy reserve, insulation, an to repel water is the- a)carbohydrate b)protein c)lipid d) nucleic acid

C) lipids.
LIPIDS – lipids are commonly called fats, oils, waxes, phospholipids, and steroids. Lipids contain large amounts of energy, most of which is stored in your body like an energy reserve. Lipids contain three elements: carbon, hydrogen, and oxygen (very little oxygen, however). Fats and oils are used as energy storage and insulation; waxes repel water (like the waxy cutin on leaves, and the peel of an apple); phospholipids are a big structural chemical, making up a large portion of the cell membrane; and steroids are units of structure and help control functions. Fats are made up of building blocks as well; a fat is made up of 3 fatty acids and 1 glycerol.