(S (S (BASENP (DT This)) (VP (VBZ is) (NP (NP (BASENP (DT the) (JJ fourth) (NN helicopter)) (VP (VBN operated) (PP (IN by) (BASENP (DT the) (NNP U.S.) (NN military))))) (SBAR (S (VP (TO to) (VP (VP (VP (VB crash)) (CC or) (VP (VB be) (VP (VBN shot) (PRT (RP down))))) (PP (IN in) (BASENP (NN two) (NNS weeks)))))))))) (PERIOD .))