Final answer:
A micronutrient is a substance needed in small quantities by the body for various physiological functions. This includes vitamins and minerals. Among the options provided, a vitamin is a micronutrient, whereas fat, protein, and water are macronutrients needed in larger quantities.
Step-by-step explanation:
Micronutrients are essential substances that our bodies need in small quantities to carry out a variety of physiological functions. They include vitamins and minerals, which play vital roles in different enzymatic reactions, immune response, and genetic material synthesis among other things. Among the options provided, vitamin is considered a micronutrient.
Fat, protein, and water are macronutrients. Macronutrients are substances needed by the body in larger quantities. They serve as our body's main energy source and contribute to the structure and function of our cells and tissues. It's important to make a distinction between these two categories in order to manage our diets effectively.
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