Final answer:
The question about the state of birth is illegal in a U.S. job interview because it could lead to national origin discrimination.
Step-by-step explanation:
Among the options provided, the question that is illegal to ask in a job interview in the United States is b. Which state were you born in? This question can be construed as discriminatory and violates Equal Employment Opportunity regulations as it may relate to an applicant's national origin, which employers are not permitted to consider in the hiring process. Asking about university attendance, possession of a commercial driver's license, or expected salary is typically legal and relevant to the job qualifications and compensation discussions.