Please give an explanation for each

Suppose that the relation SUPERVISE was created as follows:

CREATE TABLE SUPERVISE ( pssnINT REFERENCESPROFESSOR(ssn)ON DELETE NO ACTION,

gidINT REFERENCESGRADUATE(gid)ON DELETE SET NULL,

pidINT REFERENCESPROJECT(pid)ON DELETE CASCADE, PRIMARY KEY(pssn, gid, pid) );

Which of the following statements are true, and which are false?

(a) If we delete a tuple from SUPERVISE, any tuples in PROJECT referred to by this tuple are also deleted.

(b) If we delete a tuple from GRADUATE, some tuples of SUPERVISE may have their values of attribute gid set to NULL.

(c) If we try to insert a tuple into PROFESSOR, with an ssn that does not exist in SUPERVISE, the operation is rejected.

(d) If we try to insert a tuple into SUPERVISE, with a gid that does not exist in GRADUATE, the operation is rejected.