Which system asset can provide several air traffic control services in a standalone or combined manner?

The Deployable Air Traffic-Control and Landing Systems (DATCALS) is specifically designed to provide essential air traffic control services, particularly in environments where existing air traffic control infrastructure may be unavailable or damaged. DATCALS can operate independently or be combined with other systems to ensure the functionality required for safe air traffic operations. Its flexibility and mobility allow for rapid deployment in various conditions, making it instrumental in military operations and emergency situations.

In contrast, the other options serve different primary functions. For instance, the Global Command and Control System (GCCS) is focused on enhancing situational awareness and operational command and control, not directly on air traffic services. The Joint Worldwide Intelligence Communications System (JWICS) is primarily a secure communications system for intelligence data sharing rather than air traffic control. The Theater Battle Management Core System (TBMCS) is used for managing air operations but does not specifically provide the air traffic control services that DATCALS is capable of delivering. This differentiation highlights why DATCALS is the appropriate choice for the needs described in the question.