Which of the following is NOT a type of dependency (or relationship) between activities?

• A. Mandatory
• B. Discretionary
• C. Exclusionary
• D. External

Answer: (C)

Sequencing activities relies on how tasks relate to each other in time. There are three well-established dependency types: a mandatory dependency comes from the nature of the work itself, where one task physically or contractually must come before another. A discretionary dependency is a preferred sequence chosen by the project team to optimize flow, not because of a hard constraint. An external dependency involves factors outside the project’s control, such as waiting on a vendor delivery or regulatory approval. Exclusionary, however, isn’t a standard term used to describe how activities relate in a schedule. It would imply a mutual exclusion between tasks rather than a precedence relationship, and that kind of relationship isn’t part of the formal set used to sequence work. So the term that doesn’t fit as a true dependency type is Exclusionary.