1. In the university database, the relation advisor(s_id, i_id) records information about advisors of students. s_id represents student ID, i_id represents instructor ID of advisor.

a. If a student can have only one advisor, what should the appropriate primary key?

b. If a student can have more than one advisor, what should the appropriate primary key?

c. How many foreign keys? What are they?

2. In the university database, what is the result of first performing the Cartesian product of student and advisor, and then performing a select operation on the result with the prediate s_id = ID?