Which of the following is an example of a one-to-many relationship?

A one-to-many relationship occurs when a single entity from one set can be associated with multiple entities in another set. In the context of the provided choice, one teacher teaches many students illustrates this concept clearly. Here, a single teacher (the one side of the relationship) can have many students (the many side), showcasing how one entity can link to multiple counterparts.

This scenario effectively represents a one-to-many relationship as it reflects a real-world situation in educational environments where a single instructor often has multiple students to teach.

In contrast, the other choices depict various relationships that do not fit the one-to-many criterion. For instance, a single student enrolling in multiple courses exemplifies a many-to-many relationship because one student can indeed associate with multiple courses, but those courses may also have multiple students enrolled. Similarly, one book authored by multiple authors also describes a many-to-many relationship, as one book can have several authors, and authors can write multiple books. Lastly, one class containing only one student represents a one-to-one relationship, indicating that one class is linked to just one specific student, rather than multiple students.