(S (S (BASENP (JJ Iranian) (NNS authorities)) (VP (VBP have) (VP (VBN released) (NP (BASENP (NN five) (JJ British) (NNS yachtsmen)) (SBAR (WHNP (WP who)) (S (VP (VBD were) (VP (VP (VBN detained) (BASENP (JJ last) (NN week))) (PP (IN in) (BASENP (DT the) (NNP Persian) (NNP Gulf))))))))))) (PERIOD .))