## Core Concept
The Recommended Dietary Allowances (RDA) is a dietary guideline that represents the average daily intake level of a nutrient that meets the nutrient requirements of 97-98% of healthy individuals in a specific life stage and gender group. RDAs are part of the Dietary Reference Intake (DRI) system established by the National Academies of Sciences, Engineering, and Medicine. They are used to plan and evaluate nutrient intake for healthy individuals.

## Why the Correct Answer is Right
The statement that is true about RDA is that it is the average daily intake level of a nutrient that meets the nutrient requirements of 97-98% of healthy individuals in a specific life stage and gender group. This definition inherently suggests that RDAs are set to cover the needs of nearly all (97-98%) healthy individuals in a particular group, making them useful for nutritional planning.

## Why Each Wrong Option is Incorrect
- **Option A:** Without the specific details of option A, we cannot directly address its inaccuracies. However, any statement contradicting the definition and purpose of RDA would be incorrect.
- **Option B:** Similarly, without specifics, we can't directly refute, but if it suggests RDA applies to all individuals regardless of health status or doesn't account for variability, it would be wrong.
- **Option C:** If this option suggests that RDA is set to meet the needs of only 50% of the population, it would be incorrect because RDA aims to meet the needs of 97-98%, not half.

## Clinical Pearl / High-Yield Fact
A key point to remember is that RDAs are used for planning diets for individuals and are not meant to be an average intake for a group over time. They are higher than the Estimated Average Requirement (EAR), which is the average daily nutrient intake level estimated to meet the nutrient requirements of half of the healthy individuals in a particular life stage and gender group.

**Correct Answer: D.**