Ans. (D). lipids weigh less and store more energy (gram for gram) than carbohydrates.
Lipids represent a class of biomolecules, made up of long hydrocarbon chains. Lipids, such as triglycerides act as major energy storage sources in plants and animals.
Lipids weigh less and contain more carbon atoms per gram as compared to carbohydrates as in carbohydrates, more oxygen is present. Due to this, lipids provide about 9 kcal (kilocalories) per gram, while carbohydrates provide about 4 kcal per gram.
Hence, it is advantageous for migratory animals to store energy in the form of lipids instead of carbohydrates.
Thus, the correct answer is option (D).