(S (S (BASENP (PRP It)) (VP (VP (VBZ is) (ADJP (JJ unknown))) (SBAR (IN if) (S (NP (EX there)) (VP (VP (VBD were) (BASENP (DT any) (JJ other) (NNS poisons))) (PP (IN in) (BASENP (PRPD his) (NN system)))))))) (PERIOD .))