Which units are part of the Marine Corps' combatant command-level service components?

The correct choice reflects the units that operate at the combatant command level within the Marine Corps structure. Marine Forces Command (MARFORCOM) is an essential component that provides forces in support of unified combatant commands. Its role includes the organization, training, and equipping of forces, ensuring they are ready to respond to any operational request from combatant commanders.

Understanding the designation of MARFORCOM as a combatant command-level service component is crucial because it exemplifies how the Marine Corps integrates its forces for combat operations and other engagements under the command of operational leaders in various geographic or functional areas. This aligns with the Department of Defense's structured approach to joint military operations, highlighting the Marine Corps's commitment to providing capable and ready forces.

The other units mentioned serve critical functions within the Marine Corps but do not fulfill the role of a combatant command-level service component. For instance, the Marine Corps Forces Reserve focuses on ensuring trained reserves are available for mobilization as needed, while the Operational Test and Evaluation Force handles the testing of new equipment and systems. The Marine Corps Combat Development Command is responsible for advancing Marine Corps capabilities through research and development, but again, none of these units operate at the same command level as MARFORCOM.