PMP exam

The question is as below, and I am stuck at this question. Please help!!!!
you and your team have just created a schedule network diagram. you have come up with the estimates and have defined the durations and subsequently have identified Critical Path. you now decide to do a "Backward Pass" through the Schedule Network Diagram by putting in Contractual Completion Date as a late finish. Please briefly explain why it happens for each situation after backward pass computation.
A. All activities have too much positive float
B. All activities have too much negative float
C. What would you do under both situation?

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