The correct answer is: Free float.
Free float is the amount of time that an activity can be delayed without delaying the start of any succeeding activities. It is calculated as the difference between the late finish of the activity and the early start of the succeeding activity.
Total float is the amount of time that an activity can be delayed without delaying the project completion date. It is calculated as the difference between the late finish of the project and the early start of the activity.
Interfering float is the amount of time that an activity can be delayed without delaying the start of any succeeding activities, but which will delay the start of some preceding activities. It is calculated as the difference between the free float and the total float.
Independent float is the amount of time that an activity can be delayed without delaying the start of any preceding or succeeding activities. It is calculated as the difference between the early finish of the activity and the late start of the activity.