Which duration type should be used?

In your project, cost and work effort is not subject to change. Which duration type should be used?

A.
Fixed Units

B.
Fixed Duration and Units/Time

C.
Fixed Units/Time

D.
Fixed Duration and Units

Explanation:
Cost and work is here least flexible. If total work effort or fixed costs are most
important, choose Fixed Units.
Note: Working with Duration Types
Duration type options
Duration type determines whether the schedule, resource availability, or cost is most inflexible
when calculations are performed to reflect activity progress. Duration type affects update
calculations only when resources are assigned to an activity.
Choose a duration type based on which factor is the most important, or least flexible, in planning

your project.
If schedule is most important, choose Fixed Duration and Units/Time or Fixed Duration and Units.
If resource availability is most important, choose Fixed Units/Time.
If total work effort or fixed costs are most important, choose Fixed Units.