( Scientists ( ( think ( that ( protists ( are ( the ( oldest eukaryotes ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Scientists)) (VP (VBP think) (SBAR (IN that) (S (NP (NNS protists)) (VP (VBP are) (NP (DT the) (JJS oldest) (NNS eukaryotes)))))) (. .)))
Scientists think that protists are the oldest eukaryotes.
(ROOT (S (NP (NNS Protists)) (VP (VBP are) (VP (VBN thought) (S (VP (TO to) (VP (VB be) (NP (DT the) (JJS oldest) (NNS eukaryotes))))))) (. .)))