cell phones , guns , and the internal combustion engine 
(ROOT (NP (NP (NN cell) (NNS phones)) (, ,) (NP (NNS guns)) (, ,) (CC and) (NP (DT the) (NML (JJ internal) (NN combustion)) (NN engine))))
(ROOT (NP (NP (NN ) (NNS )) (, ) (NP (NNS )) (, ) (CC ) (NP (DT ) (NML (JJ ) (NN )) (NN ))))