Exam 1z0-052 topic 3 question 68 discussion

You have to create a table, STUDENTS, with the columns: STUDENT_ID, STUDENT_NAME, DATE_OF_BIRTH, and COURSE_ID.
The following constraints have to be enforced on this table:
1) Each student must be uniquely identifiable by the STUDENT_ID.
2) STUDENT_ID column should not be left blank.
3) The student should not be less than 15 years of age.
4) The student can only take a course that is specified in the COURSE table in the database.
Which three constrains must be explicitly enforced on this table? (Choose three.)