( Reef-building ( ( corals . ) '' ) )
(ROOT (S (NP (NN Reef-building)) (VP (VBZ corals)) (. .) ('' '')))
Reef-building corals."
(ROOT (S (NP (NNS Corals)) (VP (VBP build) (NP (NP (JJ hard) (NNS exoskeletons)) (SBAR (WHNP (WDT that)) (S (VP (VBP grow) (S (VP (TO to) (VP (VB become) (NP (NN coral) (NNS reefs)))))))))) (. .)))