Which type of publication applies to both the Marine Corps and the Army?

The choice identified as Multi-Service publication is applicable to both the Marine Corps and the Army because it is specifically designed to provide guidance and standards that are relevant to multiple branches of the U.S. armed forces. These types of publications ensure interoperability and unified procedures across different military services, facilitating joint operations and cohesive strategies.

In contrast, the other options are branch-specific publications. Army Directives are intended exclusively for the Army, while Marine Corps Orders serve only the Marine Corps. Navy Standard Procedures, as suggested by their name, are focused on the Navy's practices and do not extend their applicability to the other services. Therefore, Multi-Service publications are essential resources for promoting collaboration and standardization among diverse military entities.