( ( For example ) ( , ( ( if ( ( an atom ) ( has ( six protons ) ) ) ) ( , ( it ( ( ( can only ) ( be carbon ) ) . ) ) ) ) ) )
(ROOT (S (PP (IN For) (NP (NN example))) (, ,) (SBAR (IN if) (S (NP (DT an) (NN atom)) (VP (VBZ has) (NP (CD six) (NNS protons))))) (, ,) (NP (PRP it)) (VP (MD can) (ADVP (RB only)) (VP (VB be) (NP (NN carbon)))) (. .)))
For example, if an atom has six protons, it can only be carbon.
(ROOT (S (NP (DT All) (NN carbon) (NNS atoms)) (VP (VBP have) (NP (CD six) (NNS protons))) (. .)))