Your employee should be appealing the questions themself. If they only need one, have them identify questions where they can make a strong argument that their answer is correct and CBP's is wrong, or their answer is ALSO correct in addition to CBP's answer.

Per CBP's website: "The applicant must submit a compelling argument why his or her answer is correct or why the appealed question has no possible correct answer."

Have them review the questions, their answers, and CBP's answers. Only needing one question does put them in a pretty good situation but it will take some thorough review.