Answer:
D. You avoid talking about discretionary income to a room of senior citizens on a fixed income
Step-by-step explanation:
Constraints are those factors that "restrict the persuasive strategies or opportunities available to a speaker or writer". Sources of constraint include "beliefs, attitudes, documents, facts, tradition, image, interests, motives and the like."
A fixed income would become a source of constraint when talking about discretionary income to a room of senior citizens on a fixed income.
Reference: Nordquist, R. (2019). What Are Constraints in Rhetoric?. [online] ThoughtCo.