a afraid parents , , refer the back muscle .
(ROOT_0 (S_0 (ATS_3 (NP_1 (ATNP_2 (ATNP_2 (ATNP_1 (DT_0 a) (JJ_1 afraid)) (NNS_0 parents)) (COMMA_0 ,)) (COMMA_0 ,)) (VP_4 (VBP_0 refer) (NP_6 (ATNP_1 (DT_0 the) (JJ_1 back)) (NN_1 muscle)))) (DOT_0 .)))