Suppose the following method is added to the SLLStack data structure: What operation is the method doing? Removing every other node from the stack. Searching for an element. Determining the grandparent of each node. Reversing the stack. Question 6 (1 point) What is the costliest operation in a singly-linked list? Removing an inner node (i.e. not head or tail) Adding at the head or tail. Removing from the head of the list. Removing from the tail of the list