Officer Candidates must pass a series of tests before being admitted into the Officer Candidate School. An Officer Selection Officer (OSO), usually a Captain, meets with a prospective Officer Candidate. Upon completing a satisfactory interview, the OSO then makes the decision to move the prospective candidate onto the next step. The prospective candidate then must complete a short essay about why they want to be a Marine Officer, provide identification (usually a birth certificate and Social Security card), pass a background check, provide five letters of recommendation, and complete a physical medical exam.