39-

The query that displays all courses in semester 20202 in descending order :

a.

select course_id from courses order by course_id desc intersect select course_id from registration where semester_id=20202 ;

b.

select course_id from courses order by course_id desc intersect select course_id from registration where semester_id=20202 order by course_id desc;

c.

select course_id from courses intersect select course_id from registration where semester_id=20202 order by course_id;

d.

select course_id from courses intersect select course_id from registration where semester_id=20202 order by course_id desc;

40-

The query that displays courses with no students registered in it :

a.

select course_id from courses minus select course_id from registration;

b.

select course_id from registration minus select course_id from courses;

c.

select course_id from courses intersect select course_id from registration;

d.

select course_id from registration union all select course_id from courses;