11. Which normal form deals with removing multi-valued dependencies (MVDs)?

A. BCNF
B. 4NF
C. 3NF
D. 2NF

Answer: B
Explanation:

4NF is specifically concerned with eliminating non-trivial multi-valued dependencies that cause redundancy.

What is multivalued dependency?

Multivalued dependency (MVD) is a type of functional dependency that happens when two attributes in a table are independent of each other but both depend on a third attribute in that table. In other words, for a single value of one attribute, multiple independent values of another attribute can exist.

12. If instructor → course holds and also instructor → office, storing both in same table leads to:

A. Update anomaly
B. Lossless join
C. No anomaly
D. Query anomaly only

Answer: A
Explanation:

Redundancy where instructor appears multiple times (for multiple courses) can cause update anomalies when office is updated in some rows but not others.

13. Which of the following pairs must hold true for a good decomposition?

A. Lossless join & redundancy retention
B. Lossless join & dependency preservation
C. Only dependency preservation
D. Neither required

Answer: B
Explanation:

A desirable decomposition is lossless (to avoid information loss) and dependency preserving (to allow enforcement of FDs without expensive joins).

14. If R is in 3NF and all dependencies have the LHS as superkeys, then R is also in:

A. BCNF
B. 4NF
C. 1NF only
D. DKNF

Answer: A
Explanation:

BCNF requires every FD to have a superkey on the LHS. If all FDs already have LHS as superkeys, R meets BCNF.

15. Which FD pattern often indicates a transitive dependency? A → B, B → C

A. C is prime attribute
B. A → C too
C. B is non-key attribute
D. C depends on A indirectly

Answer: C
Explanation:

A → B and B → C indicate a transitive chain; if B is a non-key attribute, then C transitively depends on A through B — a classic transitive dependency.

16. Design where the key attribute determines a non-key attribute directly is:

A. Fully dependent
B. Partially dependent
C. Transitively dependent
D. Multivalued dependent

Answer: A
Explanation:

When a non-key attribute depends on the whole key (not on a part), it is called fully dependent — the desirable situation for 2NF.

17. The primary aim of normalization is:

A. Minimize tables
B. Reduce redundancy + avoid anomalies
C. Increase number of attributes
D. Improve indexing

Answer: B
Explanation:

Normalization's goal is to reduce data redundancy and avoid insertion/update/delete anomalies — improving data integrity.

18. A table with attributes (Student, Project, Mentor) where a student can have multiple projects independently of mentors shows:

A. BCNF violation
B. 4NF violation
C. 5NF violation
D. 2NF violation

Answer: B
Explanation:

Independent multi-valued facts (Student →> Project and Student →> Mentor) cause redundancy that 4NF targets. So this indicates a 4NF violation.

19. FD A,B → C but C → A also exists. What is true?

A. {A,B} is only key
B. C is also a key
C. No key exists
D. A determines BC

Answer: A
Explanation:

From AB→C and C→A, AB+ = {A,B,C}, so AB is a key. C+ = {C,A} but not B, so C alone isn't a key. Thus {A,B} is the key.

20. Which decomposition type can break some functional dependencies, though lossless?

A. 2NF decomposition
B. 3NF decomposition
C. BCNF decomposition
D. Join dependency decomposition

Answer: C
Explanation:

Decomposing to BCNF can guarantee lossless joins but may not preserve all original FDs, i.e., dependency preservation can be lost.