( ( ( Two ( outer layers ) ) ( surrounding ( a ( central core ) ) ) ) . )
(ROOT (NP (NP (CD Two) (JJ outer) (NNS layers)) (VP (VBG surrounding) (NP (DT a) (JJ central) (NN core))) (. .)))
Two outer layers surrounding a central core.
(ROOT (S (NP (NP (DT The) (NN pleura)) (SBAR (WHNP (WDT that)) (S (VP (VBZ surrounds) (NP (DT the) (NNS lungs)))))) (VP (VBZ consists) (PP (IN of) (NP (CD two) (NNS layers)))) (. .)))