, sex with strangers is a success . 
(ROOT (S (, ,) (NP (NP (NN sex)) (PP (IN with) (NP (NNS strangers)))) (VP (VBZ is) (NP (DT a) (NN success))) (. .)))
(ROOT (S (, ) (NP (NP (NN )) (PP (IN ) (NP (NNS )))) (VP (VBZ ) (NP (DT ) (NN ))) (. )))