Final answer:
Vitamins must be obtained from food because the body cannot synthesize them sufficiently. These essential micronutrients, which come in fat-soluble and water-soluble forms, are crucial for metabolic processes and are not stored long-term by the body. Therefore, the correct option is A.
Step-by-step explanation:
Nutrients that must be obtained from food because the body can't manufacture them fast enough to meet physiological needs are vitamins. Vitamins are organic compounds that are essential in very small quantities for the maintenance of normal metabolism. Unlike some amino acids that can be synthesized by the body, all vitamins must be ingested through our diet as the body does not have the capability to produce them at sufficient levels, if at all. Vitamins are classified as micronutrients and come in two categories: fat-soluble and water-soluble. These essential nutrients are necessary for various metabolic pathways and since they are not stored by the body for long periods, regular intake through food is paramount.