Final answer:
Social Security is NOT included as a protected class under the Equal Credit Opportunity Act, making option D the correct answer.
Step-by-step explanation:
The Equal Credit Opportunity Act (ECOA) is a federal law that prohibits creditors from discriminating against credit applicants on various bases, including race, color, religion, national origin, sex, marital status, and age (provided the applicant has the capacity to enter into a binding contract), as well as because all or part of the applicant's income derives from any public assistance program. However, the act does not include Social Security as a protected class. Hence, the correct answer to the question of which of the following is NOT included as a protected class by the Equal Credit Opportunity Act is D. Social Security.