Which of the Following Correctly Initializes a Doubly Linked List

Multiple Choice

Which of the following correctly initializes a doubly linked list in the default constructor?

A) head = nullptr;
Back = nullptr;
B) head = 0;
Back = 0;
Count = 0;
C) first = 0;
Last = 0;
D) first = nullptr;
Last = nullptr;
Count = 0;