Final answer:
The blank is the amount of nutrients needed by half of the people in any one age group, for example, middle-aged women.
Step-by-step explanation:
The blank is the amount of nutrients needed by half of the people in any one age group, for example, middle-aged women. The answer is a) Median nutrient requirement. The median represents the middle value in a set of data, and in this case, it denotes the amount of nutrients needed by half of the people in a specific age group.