What measure allows for the integration of air-to-surface lethal attacks?

The correct answer is the Kill Box, which is a specifically designated area in the airspace used to integrate and conduct air-to-surface lethal attacks. It serves as a pre-coordinated area where forces can operate and execute strikes without the need for further coordination or clearance, streamlining the engagement process. Kill Boxes provide a clear framework for ground and air forces to operate safely, ensuring that all participants are aware of the designated space for attacks, thus enhancing operational efficiency and effectiveness.

In contrast, a No Fire Area is a designated zone where no fire can occur, thereby preventing any lethal engagement. The Coordinated Fire Line is a specific line beyond which conventional artillery can fire without additional coordination, primarily for surface-to-surface engagements, and it doesn't apply to air-to-surface strikes. A Restrictive Fire Area imposes certain limitations on fire support to protect friendly forces or critical assets; however, it does not facilitate the integration of lethal air attacks in the same manner as a Kill Box. Thus, the other options do not provide the same level of operational flexibility or integration for air-to-surface operations as a Kill Box does.