For FMLA purposes, who’s a ‘key employee’?

Q. On the U.S. Department of Labor’s Form WH-381 (Notice of Eligibility and Rights & Responsibilities), there is a line that asks if the worker is a “key employee” as defined in the FMLA. I don’t want to offend any of our employees, so I always check the “yes” box.  Am I doing the right thing?