(S (S (BASENP (PRP It)) (VP (VBZ is) (NP (NP (BASENP (DT the) (JJS deadliest) (NN mining) (NN accident)) (PP (IN in) (BASENP (DT the) (NNP United) (NNPS States)))) (PP (IN since) (BASENP (NN 1984)))))) (PERIOD .))