Which description of a 3NF transitive dependency violation is correct?

• A. A -> B, B -> C implies A -> C and C depends on a non-key A through B.
• B. 3NF allows transitive dependencies as long as C is a candidate key.
• C. 3NF eliminates all functional dependencies.
• D. Transitive dependencies are allowed when B is a primary key.

Answer: (A)

In 3NF, non-prime attributes should depend directly on a candidate key, not through another non-key attribute. If you have A -> B and B -> C, then C is determined by A via B, which is a transitive dependency. If B is not a key and C is not a prime attribute, this means C depends on A through B, violating 3NF. That description matches the violation exactly: a non-prime attribute ends up dependent on a key through another attribute, rather than directly on the key. The other statements misstate 3NF—3NF is not about eliminating all dependencies, and transitive dependencies aren’t allowed only because a particular attribute is a key; rather, they are disallowed when a non-prime attribute would depend on a key through another non-key attribute.