Which of the following provides face-to-face intervention during a crisis as part of the ACI lines?

The choice that provides face-to-face intervention during a crisis as part of the ACI lines is Mobile Crisis Response. This service is specifically designed to respond to individuals in crisis by sending trained professionals directly to the location of the individual. This immediate, on-the-scene intervention can help stabilize the situation, offer support, and connect individuals with necessary resources and treatment.

In contrast, the other options do not involve face-to-face interactions during a crisis. Next Day Appointments refer to scheduled consultations that occur after the immediate crisis has passed, while 24-hour "live" phone response provides telephonic support but does not offer in-person assistance. Long-term outpatient therapy is oriented towards ongoing treatment and does not address immediate crisis situations.