Who does the JFC usually exercise operational control through?

The correct response highlights that the Joint Force Commander (JFC) typically exercises operational control through service component commanders. This structure allows the JFC to leverage the distinct capabilities and resources of each service branch effectively, ensuring that operations are coordinated in alignment with the overall strategic objectives of the joint force.

Service component commanders are responsible for specific areas of operation based on their respective service's strengths and are tasked with executing the mission within their assigned duties. By establishing this chain of command, the JFC can maintain effective oversight and direction across different branches while allowing for specialized operational strategies tailored to each service's unique capabilities.

In contrast to this, other options do not accurately reflect the typical command structure of a JFC. Combatant commanders have a broader role, often overseeing multiple joint task forces, while joint task force leaders operate within a more limited scope compared to the overall authority of a JFC. Field commanders typically refer to commanders in ground-level situations rather than acting as a conduit for the JFC's operational control.