Final answer:
Enlisted applicants at E-4 and below who become officer candidates are advanced to the pay grade of O-1 upon reporting to OCS, which correspond to Ensign or Second Lieutenant in the military.
Step-by-step explanation:
When E-4 and below enlisted applicants are designated as officer candidates and report to Officer Candidate School (OCS), they are typically advanced to the pay grade of O-1, also known as an Ensign in the Navy or a Second Lieutenant in other branches of the Armed Forces. The progression through military ranks is quite structured, mirroring the civilian General Schedule (GS) in its delineation of education, skills, and experiences required for different levels. For someone entering through ROTC or OCS, the career progression may start from such an officer rank, with increases in responsibility and potential advancements through the ranks depending on their performance and the leadership qualities displayed.