at his best classes charge gave Quechua .
(ROOT_0 (S_0 (ATS_3 (ATS_1 (PP_1 (IN_1 at) (NP_2 (ATNP_0 (PRPDOLLAR_0 his) (JJS_0 best)) (NP_4 (NNS_1 classes)))) (NP_5 (NN_3 charge))) (VP_3 (VBD_0 gave) (NP_3 (NNP_1 Quechua)))) (DOT_0 .)))