sustain a reasonable degree of suspense on its own 
(ROOT (VP (VB sustain) (NP (NP (DT a) (JJ reasonable) (NN degree)) (PP (IN of) (NP (NN suspense)))) (PP (IN on) (NP (PRP$ its) (JJ own)))))
(ROOT (VP (VB ) (NP (NP (DT ) (JJ ) (NN )) (PP (IN ) (NP (NN )))) (PP (IN ) (NP (PRP$ ) (JJ )))))