what boulders , a surfers a boy , you saw moved .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (ATS_2 (SBAR_0 (WHNP_0 (WP_0 what)) (S_2 (NP_1 (ATNP_0 (NP_4 (NNS_1 boulders)) (COMMA_0 ,)) (NP_6 (DT_0 a) (NNS_1 surfers))) (NP_5 (DT_0 a) (NN_2 boy)))) (COMMA_0 ,)) (NP_0 (PRP_1 you))) (VP_3 (VBD_1 saw) (VP_2 (VBN_0 moved)))) (DOT_0 .)))