( What ( ( corals ( build ( reefs 2 ) ) ) . ) )
(ROOT (S (NP (WP What)) (VP (VBZ corals) (VP (VB build) (NP (QP (CD reefs) (CD 2))))) (. .)))
What corals build reefs 2.
(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)))))))))) (. .)))