Metabolism

Step 1: Understanding energy yield.
Fat yields the highest amount of energy per gram upon oxidation compared to carbohydrates and proteins. This is because fats are more reduced, containing more hydrogen atoms, which produce more energy when oxidized.
Step 2: Analyzing the options.
(1) Starch: Starch is a carbohydrate and yields less energy per gram compared to fats.
(2) Fat: Correct — Fats contain more carbon-hydrogen bonds, which release more energy during oxidation.
(3) Glycogen: Glycogen is a polysaccharide but provides less energy per gram than fats.
(4) Protein: Proteins provide less energy per gram than fats and are not the preferred energy source.
Step 3: Conclusion.
The correct answer is (2) Fat, as it provides the most energy per gram during oxidation.