The worst-case time complexity of an ADD operation in a linked list is O(1) if adding at the beginning or end with a maintained tail reference, but it is O(N) if inserting at a specific position without extra data to assist in access.
The question pertains to the time complexity of the ADD operation in a list data structure that is implemented using linked cells, typically referred to as a linked list, and contains N elements. The worst-case time complexity of adding an element to a linked list depends on where in the list the addition is performed. If the element is added at the beginning of the list or at the end and a reference to the tail (the last element) of the list is maintained, the ADD operation can be completed in constant time, O(1). However, if a new element needs to be added to a specific position in the list, not at the beginning or end, and no additional data is stored to help with the access, it may require traversing the list to find the correct spot, leading to a time complexity of O(N) in the worst case.