If you can create 2-D arrays, can you create 3-D arrays or multiple-dimensional arrays? Can you create an array that has different numbers of columns in each row? The answer is Yes.
B. Watch (slides)
C. Try this:
Assume there are three high schools, each has four classes of freshman through senior. A number of 2 to 5 students are randomly picked from each class at each school. Create a 3-D ragged array to store each student's GPA and calculate the average GPA of each class at each school, then the average GPA of the three schools. You can make up the GPA data for each student.