Assume pointer variable p points to node x of a linked list, and node x$\text{'}$s next pointer points to node y$.$ What does free$($p$)$ operation mean?

Group of answer choices

return the memory held by x and by y to the free memory pool.

return the memory held by x to the free memory pool.

set pointer p to $0.$

return the memory held by x to the free memory pool and set pointer p to $0.$