Want to know why D option time complexity is O (n)

On the length of n..., delete the first element, the algorithm's time complexity is O (n),

(2)

A

Only tables with header node in the tail pointer loop singly linked list

B

Only with a header node pointer the meter loop singly linked list

C

Only the header pointer loop without header node singly linked list

D

Only tables without header nodes of the tail pointer loop singly linked list