(1) If there are m ' students and n ' courses such that different students may be enrolled in different courses, then the enrollment of all students in these courses can be represented by a single two-dimensional array. (2) If there are p^(') courses and q^(') instructors such that some courses have multiple sections and different instructors may teach different sections of the same course, then the assignment of all instructors to courses can be represented by a single two-dimensional array. (3) Sorting the numbers in a list in non-increasing order helps later in efficiently finding if the given number is in that list or not. (4) A binary tree is a tree in which each node except the root