An unknown sample known to contain either triglycerides or phospholipids is placed in water. The sample forms a separate layer on top of the water, with no mixing in the bulk volume of water. What type of lipid does the sample contain, and what structural element is responsible for the sample’s behavior in water? a. Triglycerides, double bonds in fatty acid tails b. Triglycerides, ester linkages c. Triglycerides, long-chain hydrocarbon tails d. Phospholipids, ester linkages e. Phospholipids, glycerol backbone