the limits of what a film can be , 
(ROOT (NP (NP (DT the) (NNS limits)) (PP (IN of) (SBAR (WHNP (WP what)) (S (NP (DT a) (NN film)) (VP (MD can) (VP (VB be)))))) (, ,)))
(ROOT (NP (NP (DT ) (NNS )) (PP (IN ) (SBAR (WHNP (WP )) (S (NP (DT ) (NN )) (VP (MD ) (VP (VB )))))) (, )))