Behind boulders , his knees asked .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (ATS_2 (PP_2 (IN_0 Behind) (NP_3 (NNS_1 boulders))) (COMMA_0 ,)) (NP_0 (PRPDOLLAR_0 his) (NNS_0 knees))) (VP_3 (VBD_0 asked))) (DOT_0 .)))