Final answer:
Sugar is not an essential nutrient because the body can generate energy from other sources, unlike Vitamin C, protein, and water, which are essential and cannot be synthesized by the body.
Step-by-step explanation:
The answer to the question 'Which of the following is not an essential nutrient?' is d) Sugar. An essential nutrient is one that cannot be synthesized by the body and must be obtained from the diet because they are crucial for proper body function. Sugar is not an essential nutrient because the body can generate energy from other sources, unlike Vitamin C, protein, and water, which are essential and cannot be synthesized by the body.
Vitamins like Vitamin C, water, and proteins are all essential nutrients. Vitamin C is a water-soluble vitamin necessary for the maintenance of connective tissue, protein and water are critical for various body functions such as building and repairing tissues and maintaining hydration levels, respectively. Sugar, however, is not categorized as an essential nutrient because the body can produce enough energy from other nutrients.