The answer is $($d$)$ none of the above. Here$$s why:

The Third Normal Form $(3$NF$)$ is a database schema design approach for relational databases which eliminates the duplication of data. This is done by ensuring that every non$-$prime attribute is non$-$transitively dependent on every candidate key of the table.

Multiple candidate keys: $3$NF can handle multiple candidate keys. Each candidate key will have its own set of attributes that are fully functionally dependent on it$.$

Candidate keys that are composite: $3$NF can also handle composite candidate keys. The non$-$prime attributes must be fully functionally dependent on the whole composite key, not on any of its subsets.

Overlapped candidate keys: Even if candidate keys overlap, as long as each non$-$prime attribute is fully functionally dependent on each candidate key, the relation is in $3$NF$.$