The correct answer is C. Free float.
Free float is the amount of time by which an activity can be delayed without delaying the start of any succeeding activities. It is calculated by subtracting the total float of the succeeding activity from the late start of the current activity.
Total float is the amount of time by which an activity can be delayed without delaying the project completion date. It is calculated by subtracting the early finish of the project from the late start of the activity.
Interfering float is the amount of time by which an activity can be delayed without delaying the start of any succeeding activities, but it will delay the start of some preceding activities. It is calculated by subtracting the total float of the preceding activity from the late start of the current activity.
Duration is the length of time required to complete an activity. It is calculated by adding the estimated time for each task in the activity.
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