QUESTION 18 What is an abstract data type (ADT)? a.It is a data type that is provided by the compiler D. An ADT is a data type described by pre-defined user operations, such as "insert data at rear" without ?? indicating how each operation is implemented; i.e., separating the interface from the implementation. C. It is a data type that can only be created by the pre-processor d. It is only used to implement a Linked list, stack, or queue QUESTION 19 What is the first thing you should define when working with a recursive function? a. The name of the function. . The base case or how the function will terminate . What color the font is in your editor. d.The return type