X → Y is broken by the X values that come with more than one Y value. A query with GROUP BY and COUNT(DISTINCT …) finds them.

1. Test building → dept on staff_directory. Return each building that breaks it.
2. Does the data break dept → building?
3. Which phone_ext breaks phone_ext → emp_id?

The last two tasks need no query. R(A, B, C, D, E) has these FDs:

A → C
C → D
BD → E

4. What is A+?
5. Which two attributes together are a candidate key of R?