Which of the following calculates the exact height of an AVL tree?

A$.$

if $($node $==$ null$)$

return $-1$ ;

return : FUN $($node: node. left$),$ b: FUN $($node: node.right$))$ ;

B$.$

if $($node $==$ null$)$

return $0$ ;

return max $($a: FUN $($node: node. left$),$ b: FUN $($node: node.right$))$ ;

c$.$

if $($node $==$ null$)$

return $($node: node. left$),$ b: FUN$($node: node.right$))$;

return $-1$ ;

D$.$ if $($node $==$ null$)$

return $0$ ;

return FUN $($node: node. left$),$ b: FUN$($node: node.right$))$;