Which of the following is not a valid approach to implementing a SortedList

• Write it from scratch, most of the methods implemented similarly to the List implementation, some methods removed, added, or updated to ensure that the List remains in sorted order
• Use composition, where a SortedList uses a List as a field, with other attributes and methods to supported the SortedList features
• Use inheritance, where a SortedList is a child (subclass) of a List (superclass). Attributes and methods are inherited, methods overridden and updated to ensure that the List remains in sorted order. Methods which do not suit the sorted requirement are be overridden with code which throws an Exception if called