Which XXX completes the C$++$ AVL tree Node class's GetBalance$()$ function?

int GetBalance$()\{$

int leftHeight $=-1$;

if $($left$)\{$

leftHeight $=$ left$->$height;

$\}$

int rightHeight $=-1$;

if $($right$)\{$

rightHeight $=$ right$->$height;

$\}$

return XXX;

$\}$

Group of answer choices

leftHeight $-$ rightHeight

leftHeight $+$ rightHeight

max$($leftHeight$,$ rightHeight$)$

min$($leftHeight$,$ rightHeight$)$