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Third Normal Form - Quiz

Select the best answer or answers for each question.
1. For every nontrivial functional dependency X → A, which condition defines third normal form (3NF)? Please select the best answer.
  A. X is a superkey, or A belongs to at least one candidate key.
  B. X must always be the chosen primary key.
  C. Every column must contain unique values.
  D. The table must contain no foreign keys.

2. Which statements about deliberate denormalization are correct? Please select all the correct answers.
  A. It guarantees faster execution of every query.
  B. It can improve selected reads by storing redundant or precomputed information.
  C. It can reduce repeated join or aggregation work for a particular workload.
  D. It requires a maintenance policy for keeping derived information sufficiently current.

3. Which statements about normal forms are correct? Please select all the correct answers.
  A. 2NF excludes dependencies of non-prime attributes on a proper subset of any candidate key.
  B. A table in 2NF can still repeat department names because DepartmentID determines DepartmentName.
  C. 4NF requires the determinant of every nontrivial multivalued dependency to be a superkey.
  D. Adding a surrogate primary key automatically places a table in 3NF.

4. Teaching(StudentID, CourseID, InstructorID) has the dependencies (StudentID, CourseID) → InstructorID and InstructorID → CourseID. The candidate keys are (StudentID, CourseID) and (StudentID, InstructorID). An instructor can teach many students. Under these dependencies, which statement is correct? Please select the best answer.
  A. The relation violates 2NF because its candidate keys are composite.
  B. The relation satisfies 3NF but violates BCNF.
  C. The relation satisfies BCNF because every attribute is prime.
  D. The relation violates 1NF because InstructorID can repeat.

5. Which statements about verifying a decomposition are correct? Please select all the correct answers.
  A. A lossless decomposition reconstructs the original relation by joining its projections without introducing spurious rows.
  B. Dependency preservation allows the original functional dependencies to be enforced through dependencies in the individual relations.
  C. A lossless BCNF decomposition always preserves every original functional dependency.
  D. A successful join of a few sample rows proves losslessness for every valid database instance.