21. In a university, a course can have multiple instructors, and each instructor can teach multiple courses. How should this be modeled?

A. One-to-one relationship
B. One-to-many relationship
C. Many-to-many relationship
D. Recursive relationship

Answer: C
Explanation:

This is a many-to-many relationship between Course and Instructor. An associative entity may be used to store additional attributes like teaching semester.

22. In a hospital ER model, “Room Number” is assigned based on patient type (ICU, General). How should Room Number be represented?

A. Simple attribute
B. Derived attribute
C. Multivalued attribute
D. Composite attribute

Answer: D
Explanation:

Room Number can be a composite attribute consisting of building, floor, and room sequence.

23. In an e-commerce system, a product may belong to multiple categories, and each category contains multiple products. How should this relationship be represented?

A. One-to-one
B. One-to-many
C. Many-to-many
D. Derived relationship

Answer: C
Explanation:

This is a many-to-many relationship between Product and Category, typically implemented with an associative entity.

24. In a company, a project can have multiple tasks, and each task is assigned to exactly one project. How should Task be represented?

A. Strong entity
B. Weak entity
C. Derived attribute
D. Multivalued attribute

Answer: B
Explanation:

Task depends on the existence of a Project, making it a weak entity identified by a partial key plus the project key.

25. In a university ER model, “Email” of a student can be computed from student ID and domain. How should it be represented?

A. Simple attribute
B. Multivalued attribute
C. Derived attribute
D. Weak entity

Answer: C
Explanation:

“Email” is a derived attribute because it can be calculated from other stored attributes like student ID and domain.

26. In a library, a “Borrowing” record links a student and a book with the borrow date. What type of entity should “Borrowing” be?

A. Strong entity
B. Associative entity
C. Weak entity
D. Multivalued attribute

Answer: B
Explanation:

“Borrowing” is an associative entity connecting Student and Book and storing relationship attributes like borrow date.

27. In a hospital, an “Insurance Policy” is linked to patients. A patient can have multiple policies. How should this be modeled?

A. Weak entity
B. Derived attribute
C. Multivalued attribute
D. Simple attribute

Answer: A
Explanation:

Insurance Policy is a weak entity because it depends on the existence of a patient for identification.

28. In a university, each department can have multiple professors, and each professor belongs to exactly one department. What is this relationship type?

A. One-to-one
B. One-to-many
C. Many-to-many
D. Recursive

Answer: B
Explanation:

This is a one-to-many relationship where one department has many professors, but each professor belongs to only one department.

29. A product has multiple reviews, and each review is associated with exactly one product. How should reviews be represented?

A. Derived attribute
B. Multivalued attribute
C. Weak entity
D. Strong entity

Answer: C
Explanation:

Reviews are weak entities because they depend on the Product for existence and identification.

30. In a company, an employee can belong to multiple teams, and each team can have multiple employees. How should this relationship be represented?

A. One-to-one
B. One-to-many
C. Many-to-many
D. Derived relationship

Answer: C
Explanation:

This is a many-to-many relationship, best implemented with an associative entity linking Employee and Team.