Which FPCON applies in the immediate area where a terrorist attack has occurred or when intelligence indicates an imminent terrorist action?

The correct choice is Delta, which signifies the highest level of alert within the Force Protection Condition (FPCON) system. This condition is implemented when there is a confirmed terrorist attack in the immediate area or when there is credible intelligence that indicates an imminent threat of such an attack. In this state, military and security personnel take the most stringent measures to protect individuals and resources, including restricted access to affected areas, increased security checks, and enhanced surveillance measures.

The other options represent progressively lower levels of security preparedness. Alpha indicates a general threat level, with routine security measures. Bravo indicates an increased and more predictable threat, prompting a heightened security posture but not as severe as Delta. Charlie denotes a conditional situation where there is an elevated threat level, requiring more stringent measures than Bravo, but it does not reach the immediate response level of Delta. Therefore, Delta represents the most urgent state of readiness in terms of physical security in response to a direct threat or attack.