Given the following relational database schema:

Student = (SSN, Name, Major)

Course = ( CourseNumber, PrerequisiteCourseNumber, Course Title, NumberUnits)

Section = ( CourseNumber, Quarter, RoomNumber, DayTime), where DayTime is of the form MW 1:0-2:00PM.

Enrollment = (SSN,CourseNumber, Quarter, Grade)// Grade is either Null or a letter grade.

Express the following queries using appropriate SQL statements with a minimum number of operations:

a)List every Course title which is a prerequisite for the largest number of courses.