has been replaced by the bottom of the barrel 
(ROOT (S (VP (VBZ has) (VP (VBN been) (VP (VBN replaced) (PP (IN by) (NP (NP (DT the) (NN bottom)) (PP (IN of) (NP (DT the) (NN barrel))))))))))
(ROOT (S (VP (VBZ ) (VP (VBN ) (VP (VBN ) (PP (IN ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (DT ) (NN ))))))))))