Final answer:
None of the options (age, gender, or race) constitute a valid reason to not hire someone because discrimination based on these factors is illegal according to the EEOC unless they are considered BFOQs.
Step-by-step explanation:
The valid reason not to hire someone is D. None of the above. According to the U.S. Equal Employment Opportunity Commission (EEOC), it is illegal to discriminate against a job applicant or an employee based on race, color, religion, sex, sexual orientation, national origin, age (40 or older), disability, or genetic information. These criteria cannot legally be part of hiring decisions unless they qualify as Bona Fide Occupational Qualifications (BFOQs), which are very specific exceptions and do not apply to race. It's worth noting that there are instances where age, sex, or religion might be considered BFOQs, such as mandatory retirement ages for airline pilots for safety reasons or hiring based on sex for positions like guards in gender-specific facilities due to privacy concerns.