Which of the following best describes close air support (CAS) within joint air operations?

Close air support (CAS) is specifically defined as air action conducted against hostile targets that are in close proximity to friendly forces. The primary objective of CAS is to directly support ground troops by engaging enemy forces that pose an immediate threat, while ensuring that the safety of friendly forces is maintained. This required proximity is critical, as it allows for coordinated operations and real-time support, which can include attacking enemy troops, vehicles, or fortified positions.

In joint air operations, CAS plays a vital role by providing flexibility and responsiveness on the battlefield. It requires precise targeting and coordination to minimize the risk of collateral damage and to achieve the desired effects on enemy forces without harming friendly personnel or assets. Thus, the correct answer reflects the essence of close air support as it pertains to joint air operations.