What one character code is used with the MOS and SL to form the basic five character MOSC?

The correct answer is the Special Qualification Identifier (SQI). In military occupational specialty (MOS) designations, the basic five-character MOSC (Military Occupational Specialty Code) is formed by combining the primary MOS with a skill level (SL) and a one-character code which indicates special qualifications. The SQI is specifically the designation used to capture these special qualifications.

The function of the SQI is to identify Soldiers who possess skills that are not inherent to their primary MOS but are nonetheless valuable and applicable in specific contexts. For example, if a Soldier has additional training or certification that qualifies them for certain roles or responsibilities beyond their standard MOS, this is denoted through the SQI.

This format helps maintain a comprehensive view of an individual's capabilities and qualifications, which is essential for various personnel management and deployment decisions within the military.