the unthinkable , the unacceptable , the unmentionable 
(ROOT (NP (NP (DT the) (JJ unthinkable)) (, ,) (NP (DT the) (JJ unacceptable)) (, ,) (NP (DT the) (JJ unmentionable))))
(ROOT (NP (NP (DT ) (JJ )) (, ) (NP (DT ) (JJ )) (, ) (NP (DT ) (JJ ))))