The rules for signing documents filed with the court are here: http://www.ncga.state.nc.us/EnactedLegislation/Statutes/HTML/BySection/Chapter_1A/GS_1A-1,_Rule_11.html. Certificates of Service do not need to be notarized. Answers do not need to be notarized, either. If you are including an affidavit (sworn statement) as part of your Answer, however, it will need to be notarized.
(This response does not constitute legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter in question. Many times the questioner may leave out details which would make the reply unsuitable. The questioner should confer with an attorney about the specifics of their case.)