Which of the following operation has a worst case time complexity of O$($n$)?$

Question $14$ options:

A$)$

push$()$ to an linked list based implementation stack with only a head $($or top$)$ reference variable

B$)$

pop$()$ to an linked list based implementation stack with only a head $($or top$)$ reference variable

C$)$

None of the above

D$)$

push$()$ to an array based implementation stack with a top variable