The amount of time that an activity can be delayed from its early start date...

The time an activity can be delayed from its early start without impacting the overall project completion date is called total float.

Option A (negative float) refers to delays beyond permissible limits.

Option B (free float) refers to delays without affecting the early start of any successor.

Option D (interfering float) is a lesser-used term denoting the time available without delaying the project completion but affecting a successor’s float​.