engages us in constant fits of laughter , 
(ROOT (S (VP (VBZ engages) (NP (PRP us)) (PP (IN in) (NP (NP (JJ constant) (NNS fits)) (PP (IN of) (NP (NN laughter)))))) (, ,)))
(ROOT (S (VP (VBZ ) (NP (PRP )) (PP (IN ) (NP (NP (JJ ) (NNS )) (PP (IN ) (NP (NN )))))) (, )))