c# - LINQ の group by 句

Question

以下のコードを実行しましたが、グループ句がグループ化を行う方法を理解していません

これで助けてください。私は c# が初めてです。

public static List<Student> GetStudents()
        {
            // Use a collection initializer to create the data source. Note that each element 
            //  in the list contains an inner sequence of scores.
            List<Student> students = new List<Student>
        {
           new Student {First="Svetlana", Last="Omelchenko", ID=111, Scores= new List<int> {97, 72, 81, 60}},
           new Student {First="Claire", Last="O'Donnell", ID=112, Scores= new List<int> {75, 84, 91, 39}},
           new Student {First="Sven", Last="Mortensen", ID=113, Scores= new List<int> {99, 89, 91, 95}},
           new Student {First="Cesar", Last="Garcia", ID=114, Scores= new List<int> {72, 81, 65, 84}},
           new Student {First="Debra", Last="Garcia", ID=115, Scores= new List<int> {97, 89, 85, 82}} 
        };

            return students;

        }
List<Student> students = GetStudents();

            // Write the query. 
            var studentQuery =
                from student in students
                let avg = (int)student.Scores.Average()
                group student by (avg == 0 ? 0 : avg / 10);

StudentQuery の生成方法がわかりません。前もって感謝します 。