Hiring managers have their companies' best interests at heart. Of course they want to know if you'll be a good fit, but they also want to know if you're likely to leave to start a family or retire in the near future. But asking anything intended to get information about a person's status in a protected class—age, race, religion, pregnancy, etc.—is technically illegal. Still, Peter K. Studner, author of Super Job Search IV: The Complete Manual for Job Seekers & Career Changers, says that often both interviewers and interviewees don't realize that a certain line of inquiry has veered into murky territory. To help defend job seekers against revealing information that could be used against them, here are eight questions that you should always avoid answering.

1. Are You Married?

Anything that fishes for information about a candidate's family plans (marriage, engagement, and child planning) is technically illegal because it falls under pregnancy discrimination. It can often seem like a hiring manager is just making pleasant conversation and trying to get to know you better, but job applicants are not obligated to disclose any personal information. This could also be a subtle way to question someone about their sexual orientation—another protected class.

2. How Old Are You?

Lots of applications will stipulate that employees have to be over 18, and that's fine—ensuring their workers are not minors is within a company's rights. But this question becomes problematic when interviewers ask more mature candidates that question, because it's illegal to discriminate against anyone over 40 on the basis of age. If anyone asks, don't feel bad about declining to respond. Recognize that whoever is interviewing you probably already has some sense of your age just from looking at your resume, and use the opportunity to emphasize all those years of experience.

3. When Did You Graduate?

We all know how math works—this is just a not-so-sly way to calculate someone's age. (Feel free to nix the graduation year from your resume, too.) "If the interviewer presses for a reply, you might give him the date and then ask how that applies to your candidacy," Studner says. "And in the final analysis, would you really want to work for a company where the management discriminates against age? It might be better to move on."

4. How's Your Health?

If it's a physically demanding job, employers have a right to ask about specific physical abilities. For example: "This job requires lifting packages up to 30 pounds, or standing on your feet for six hours a day, or talking on the phone at least 80 percent of the time. Is this something you can do on a continuous basis?" But anything that isn't directly related to tasks you'll be performing on the job is personal information that you don't have to—and shouldn't—reveal.

5. What Religion Are You? Do You Observe Any Religious Holidays?

It's illegal to discuss your religion in an interview, even if it will affect your need to take time off. It can be awkward to back out of this question if an employer presses the issue, so Studner suggests a polite but firm, "I prefer not to discuss my religion, but I can assure you that it will not interfere with my doing this job."

6. Have You Ever Been Arrested?

It's not illegal to ask if you've ever been convicted of a crime, and many employers do, either on the application or in the interview. But what they can't ask about is your arrest record. That said, it is not illegal for a concerned hiring manager to do some independent research to see if there are any records of arrests available online. If you know they'll be looking into your background, this constitutes a rare instance where an interviewee should volunteer incriminating information.

"In these kinds of cases where a future employer might uncover prior arrests, it is important to discuss the incident up front and point out that it was a thing of the past, never to be repeated," Studner says. "The more serious the offense, the more convincing you have to be."

7. What Country Are You From?

As long as you're authorized to work in the country where the job is located—a question they are allowed to ask—employers can't dig into where you're from because nationality discrimination is illegal. Similarly, they can't ask if English is your first language.

8. Do You Like To Drink Socially?

It's not entirely clear why this would come up in an interview situation, but if it does, it's actually illegal in order to protect people who might answer "No." Under the Americans with Disabilities Act of 1990, recovering alcoholics don't have to reveal any information that might hint at their status. It's also illegal to question job applicants about when they last used illegal drugs, although asking if you're currently using illegal drugs is permissible.

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