Carrie phoned an applicant's former supervisor for a reference. The supervisor refuses to give any information about the former employee. What mistake may Carrie have made? She did not get a signed consent form from the applicant releasing the former supervisor from liability She contacted the supervisor by phone rather than in writing or via email, thus opening the supervisor to a charge of slander by the applicant Former supervisors rarely provide useful information $,$ so it is not an effective use of Carrie's time to pursue this contact She limited her request for information to dates of employment, positions held, and the applicant's previous job title rather than asking for particular examples of good or poor performance