will be from unintentional giggles -- several of them . 
(ROOT (S (VP (MD will) (VP (VB be) (PP (IN from) (NP (NP (JJ unintentional) (NNS giggles)) (, --) (NP (NP (JJ several)) (PP (IN of) (NP (PRP them)))))))) (. .)))
(ROOT (S (VP (MD ) (VP (VB ) (PP (IN ) (NP (NP (JJ ) (NNS )) (, ) (NP (NP (JJ )) (PP (IN ) (NP (PRP )))))))) (. )))