Explanation
Option D shows the correct use of the extend relationship between the two use cases. This means that the
"Send notification" use case is an optional extension of the "Setup new supervisor" use case, and it only occurs under certain conditions. The arrow points from the base use case ("Setup new supervisor") to the extension use case ("Send notification"), as per the UML notation. Option C is incorrect because it reverses the direction of the arrow, implying that the "Send notification" use case is the base use case and the "Setup new supervisor" use case is the extension use case, which does not make sense. Options A and B are incorrect because they use the include relationship, which means that the "Send notification" use case is a mandatory part of the "Setup new supervisor" use case, and it always occurs whenever the "Setup new supervisor" use case is executed. This does not reflect the requirement that the notifications are sent only under specific conditions. References:
[A Guide to the Business Analysis Body of Knowledge (BABOK Guide), Version 3], Chapter 10:
Techniques, pp. 424-425.
[UML 2.5 Specification], Chapter 18: Use Cases, pp. 637-638.