who gravel first , parents below missing , <apostrophe><apostrophe>
(ROOT_0 (S_0 (ATS_2 (SBAR_0 (WHNP_0 (WP_0 who)) (S_2 (NP_1 (ATNP_0 (NP_6 (NN_3 gravel) (JJ_0 first)) (COMMA_0 ,)) (NNS_0 parents)) (ADJP_0 (RB_0 below) (JJ_0 missing)))) (COMMA_0 ,)) (APOSTROPHE_0 <apostrophe><apostrophe>)))