that might have made it an exhilarating 
(ROOT (S (WHNP (DT that)) (VP (MD might) (VP (VB have) (VP (VBN made) (S (NP (PRP it)) (NP (DT an) (NN exhilarating))))))))
(ROOT (S (WHNP (DT )) (VP (MD ) (VP (VB ) (VP (VBN ) (S (NP (PRP )) (NP (DT ) (NN ))))))))