Relational Algebra

Consider two database relations, Student(Fname, Lname, MajorCode) and Instructor(First_Name, Last_Name, DeptID), where Fname/First_Name and Lname/Last_Name represent compatible character datatypes. Which of the following statements is correct regarding the relational algebra union-compatibility of these two relations?

'-- Relational algebra union compatibility check:
-- Degree(R) == Degree(S) AND Domain(R.col_i) == Domain(S.col_i)

Suppose you are given two database tables, 'Active_Students' and 'Honors_List', both containing identical, union-compatible columns. Which SQL set operator should be used to retrieve only those student records that exist in both tables concurrently?

SELECT stId, stName FROM Active_Students
INTERSECT
SELECT stId, stName FROM Honors_List;