certainly the performances are worthwhile . 
(ROOT (S (ADVP (RB certainly)) (NP (DT the) (NNS performances)) (VP (VBP are) (ADJP (JJ worthwhile))) (. .)))
(ROOT (S (ADVP (RB )) (NP (DT ) (NNS )) (VP (VBP ) (ADJP (JJ ))) (. )))