Choose ALL that apply. Command design pattern is useful for... Sending requests/commands to receiver objects, to make the receiver object perform desired actions Representing different requests/commands as separate objects Creating "redo/undo" functionality in a program Unifying different requests/commands by a common interface A concrete command can be extended to create a more specific concrete command. True False Which of the following is TRUE about Visitor design patterns This is a patter where one Visitor interface defines a computation / operation and a different class is responsible for providing data access. O Additional operations can be added externally to existing classes through the Visitor class. This pattern is useful for adding a certain capability to multiple different types of objects. All of the above The Visitor in the visitor design pattern is usually a.. O Class Abstract Class O Interface O A Class that inherits from a concrete Visitor