hit that may strain adult credibility 
(ROOT (VP (VBD hit) (SBAR (WHNP (DT that)) (S (VP (MD may) (VP (VB strain) (NP (NN adult) (NN credibility))))))))
(ROOT (VP (VBD ) (SBAR (WHNP (DT )) (S (VP (MD ) (VP (VB ) (NP (NN ) (NN ))))))))