You know by now that a stress

You know by now that a stress question is designed to make you defensive, angry, nervous, or doubtful. The best way to deal with the stress question is to remain calm and answer it in the best way you know how. Therefore, C would be the optimum choice in this example.

Illegal Questions
Ninety-five percent of interviewers will not ask you illegal questions. But some—because of ignorance, inexperience, or uncharitable motives—may ask you indirectly or directly about your marital status, number of children, arrest record, physical or mental disabilities, race, religion, sexual preference, or ethnicity.

You have a legal right not to discuss these issues. One of the best ways to get around the discomfort of these types of inquiries (other than getting up and walking out the door) is to respond as follows:

ANSWER A: Excuse me, but I’m not sure I understand. Could you please rephrase the question?

That alone will usually stop the interviewer in his or her tracks. If he or she asks again, you can say:
ANSWER A: I’m not sure how my marital status would have any bearing on my ability to carry out my job responsibilities. Could you please clarify that for me?

Or . . .
ANSWER A: Does my race have something to do with the job description? I don’t think I understand the question.

Taken from : Fearless Interviewing - How To Win The Job