Which XXX completes the Java BinarySearchTree class's remove$()$ method?

public boolean remove$($int key$)\{$

Node parent $=$ null;

Node currentNode $=$ root;

while $($XXX$)\{$

if $($currentNode$.$key $==$ key$)\{$

if $($currentNode$.$left $==$ null && currentNode.right $==$ null$)\{$

if $($parent $==$ null$)\{$

root $=$ null;

$\}$

else if $($parent$.$left $==$ currentNode$)\{$

parent.left $=$ null;

$\}$

else $\{$

parent.right $=$ null;

$\}$

return true;

$\}$

else if $($currentNode$.$left $!=$ null && currentNode.right $==$ null$)\{$

if $($parent $==$ null$)\{$

root $=$ currentNode.left;

$\}$

else if $($parent$.$left $==$ currentNode$)\{$

parent.left $=$ currentNode.left;

$\}$

else $\{$

parent.right $=$ currentNode.left;

$\}$

return true;

$\}$

else if $($currentNode$.$left $==$ null && currentNode.right $!=$ null$)\{$

if $($parent $==$ null$)\{$

root $=$ currentNode.right;

$\}$

else if $($parent$.$left $==$ currentNode$)\{$

parent.left $=$ currentNode.right;

$\}$

else $\{$

parent.right $=$ currentNode.right;

$\}$

return true;

$\}$

else $\{$

Node successor $=$ currentNode.right;

while $($successor$.$left $!=$ null$)\{$

successor $=$ successor.left;

$\}$

currentNode.key $=$ successor.key;

parent $=$ currentNode;

currentNode $=$ currentNode.right;

key $=$ successor.key;

$\}$

$\}$

else if $($currentNode$.$key $<$ key$)\{$

parent $=$ currentNode;

currentNode $=$ currentNode.right;

$\}$

else $\{$

parent $=$ currentNode;

currentNode $=$ currentNode.left;

$\}$

$\}$

return false;

$\}$

Group of answer choices

parent $==$ null

currentNode $!=$ null

currentNode $==$ null

parent $!=$ null