The correct answer is D. All the above.
The total float of an activity is the amount of time that the activity can be delayed without delaying the project finish date. The duration of an activity is the amount of time it takes to complete the activity.
If the total float and duration of an activity are 5 and 10 days respectively, then the activity can be:
- Started 5 days later. This will not delay the project finish date, because the activity has 5 days of total float.
- Completed 5 days later. This will also not delay the project finish date, because the activity has 5 days of total float.
- Performed at a slower rate in 15 days. This will also not delay the project finish date, because the activity has 5 days of total float.
In other words, the activity can be delayed by up to 5 days without delaying the project finish date. It can also be completed at a slower rate, as long as it is completed within 15 days.