(S (S (NP (BASENP (DT A) (NN leak)) (PP (IN at) (BASENP (DT an) (JJ offshore) (NN oil) (NN drilling) (NN rig)))) (VP (VBZ has) (VP (VP (VBN caused) (BASENP (DT an) (NN oil) (NN slick))) (PP (IN off) (NP (BASENP (NNP Australia) (POS 's)) (NN coast)))))) (PERIOD .))