this u-boat does n't have a captain . 
(ROOT (S (NP (DT this) (NN u-boat)) (VP (VBZ does) (RB n't) (VP (VB have) (NP (DT a) (NN captain)))) (. .)))
(ROOT (S (NP (DT ) (NN )) (VP (VBZ ) (RB ) (VP (VB ) (NP (DT ) (NN )))) (. )))