( ( This core ) ( ( is ( surrounded ( by ( ( two layers ) ( of trophoblast ) ) ) ) ) ; ) )
(ROOT (S (NP (DT This) (NN core)) (VP (VBZ is) (VP (VBN surrounded) (PP (IN by) (NP (NP (CD two) (NNS layers)) (PP (IN of) (NP (NN trophoblast))))))) (: ;)))
This core is surrounded by two layers of trophoblast;
(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)))) (. .)))