The correct answer is C. Lookup, as explicitly shown in the study guide. A Lookup relationship is Salesforce's flexible mechanism for linking records between objects where one record can be associated with another without imposing the stronger dependency characteristics of a Master-Detail relationship. This makes it appropriate for common many-to-one relationships, where many child-side records may reference one record on another object.
The key distinction is relationship strength. A Master-Detail relationship creates a tightly coupled dependency. The detail record depends strongly on the master, and the relationship can affect ownership, sharing, roll-up summaries, and deletion behavior. It should therefore be used only when those stronger semantics are actually required.
A Hierarchical relationship is a specialized relationship available for the User object and is intended to create user-to-user hierarchy relationships. It is not the general-purpose solution for linking arbitrary business objects.
For a UX Designer, data-model decisions matter because they affect how related information is displayed, edited, navigated, and maintained in the user experience. Choosing the correct relationship type allows the designer and administrator to support the intended business interaction without introducing unnecessary data dependencies.
Therefore, for the generic one-to-many or many-to-one relationship described, Lookup is the appropriate choice.
Study Guide reference/topics: Salesforce data model, Lookup relationships, object relationships, Declarative Design.
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