Our ArrayStack class implements a bounded stack. The LLNode class is a self-referential class. Our LinkedStack class implements an unbounded stack. When an object of class LinkedStack represents an empty stack, its top variable is null Multiple Choice Identify the choice that best completes the statement or answers the question We deal with ADTs on three levels. On which level do we just need to know how to u application (or user, client) logical (or abstract) machine (or assembly) implementation (or concrete) We deal with ADTs on three levels. On which level do we deal with the "how " we represent the attributes and fulfill the responsibilities of the ADT? application (or user, client) logical (or abstract) machine (or assembly) implementation (or concrete) We deal with ADTs on three levels. On which level do we just deal with the "what' what does the ADT model, what are its responsibilities, what is its interface? application (or user, client) logical (or abstract) machine (or assembly) implementation (or concrete) The following sequence of operations essentially leaves a stack unchanged pop followed by push pop followed by top Push followed by top top followed by push Objects can represent both variables and constants classes and inheritance information and behavior methods and constructors Within an object, actions are modeled using classes variables methods constants