Answer:
The free rider problem.
Step-by-step explanation:
The Free Rider problem can be defined as a burden bear on a resource that is shared commonly. This burden is because some people use or overuse this resource either by paying minimal contribution or no contribution at all to the resource.
In the given case, the group project is the shared source shared by Darin, Martin, Aaid, and Abbey. But the burden was bear by Darin only in this project. Martin, Aaid and Abbey did not contribute to the project so from the sociological lens this is an example of "the free-rider problem".
So, the correct answer is option B.