at parents heard not be , <apostrophe><apostrophe>
(ROOT_0 (S_0 (ATS_2 (SBAR_0 (IN_2 at) (S_1 (NP_1 (NNS_0 parents)) (VP_5 (ATVP_1 (VBD_0 heard) (RB_1 not)) (VP_1 (VB_0 be))))) (COMMA_0 ,)) (APOSTROPHE_0 <apostrophe><apostrophe>)))