Negative total float occurs when an activity's scheduled completion date extends beyond the project deadline due to constraints. This condition indicates that the activity is still pending and needs immediate attention to avoid further delays.
* Option A (milestone) is unrelated.
* Option B (critical path) is not necessarily true, as activities with negative float can exist off the critical path under certain constraints.
* Option C (completed in the past) is incorrect as negative float applies only to future or ongoing activities.