Which relationship is possible when two tables share the same primary key? a. one-to-one b. one-to-many c. many-to-one d. many-to-many

The correct answer is many-to-one

This kind of relationship is likely to happen when two tables share the same primary key because one entity had values that are related to another one that has distinctive values. It is usually applied by primary key relationships and the relationships normally are between fact and dimension tables and levels in hierarchy as well.  

your answer is confidentiality

this seems to be in the wrong category. but i'll take some free points my dude

posting this in wrong category will result in people seeing it who won't know the answer.