Final answer:
DRIs have not been determined for nonessential trace minerals as their functions in the body, if any, are not clearly defined and they may not be necessary for proper body function. The correct answer is option: e. nonessential trace minerals
Step-by-step explanation:
For which category have Dietary Reference Intakes (DRIs) not yet been determined? The answer is: e. nonessential trace minerals. DRIs have been established for essential major minerals and essential trace minerals due to their importance in various physiological processes and their presence in dietary sources.
Essential major minerals include substances like calcium and magnesium, which are required in larger quantities. Essential trace minerals like iron and zinc are needed in smaller quantities, but are still vital for health. DRIs for nonessential trace minerals have not been established because their functions, if any, are not clearly defined and they may not be necessary for proper body function.