Linked List Operations That Were Studied Included Adding/removing an Element

Multiple Choice

Linked list operations that were studied included adding/removing an element at the end or in the middle, and retrieving the kth element. If the iterator is currently pointing to the correct location for insertion or removal, which of the following statements about these doubly-linked list operations is correct?

A) The least expensive operation of a doubly-linked list is to add an element at the end.
B) The least expensive operation of a doubly-linked list is to retrieve an arbitrary element.
C) The least expensive operation of a doubly-linked list is to add an element in the middle.
D) All of these operations have the same time cost.