he warily be classes the lesson at a sky <apostrophe>s .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (NP_1 (PRP_0 he)) (ADVP_0 (RB_0 warily))) (VP_3 (ATVP_2 (VB_0 be) (NP_4 (NNS_1 classes))) (NP_3 (NP_5 (DT_0 the) (NN_2 lesson)) (PP_0 (IN_1 at) (NP_4 (ATNP_0 (DT_0 a) (NN_3 sky)) (POS_0 <apostrophe>s)))))) (DOT_0 .)))