Explain the public policy exception to the doctrine of employment at-will, including stating what the ex-employee must demonstrate

Please explain the public policy exception to the doctrine of employment at-will, including stating what the ex-employee must demonstrate to prevail and give at least three examples of the public policy exception that have been recognized by some of the states.

NOTE* Please read the document I attached, since the professor is very strict on plagiarism so please read the rule before starting answer the question. Thank you