what to , it is at back .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (ATS_2 (SBAR_0 (WHNP_0 (WP_0 what)) (S_2 (VP_0 (TO_0 to)))) (COMMA_0 ,)) (NP_0 (PRP_1 it))) (VP_3 (VBZ_0 is) (PP_1 (IN_1 at) (NP_2 (RB_0 back))))) (DOT_0 .)))