Final answer:
The correct term describing a group of elders for a community assessment is an aggregate, which refers to individuals grouped based on a common characteristic, in this case, age.
Step-by-step explanation:
In gathering community assessment data about concerns of the elderly, the term that best describes the group of elders in this context is an aggregate. An aggregate in public health refers to a collection of individuals who have one or more personal or environmental characteristics in common. The individuals in this scenario are grouped together for the assessment based on their age, which is the common trait they share. Therefore, the correct option is d. Aggregate.