of a boy , his parents could think on .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (ATS_2 (PP_2 (IN_0 of) (NP_5 (DT_0 a) (NN_2 boy))) (COMMA_0 ,)) (NP_0 (PRPDOLLAR_0 his) (NNS_0 parents))) (VP_3 (MD_0 could) (VP_1 (VB_0 think) (PRT_0 (RP_0 on))))) (DOT_0 .)))