could have yielded such a flat , plodding picture 
(ROOT (VP (MD could) (VP (VB have) (VP (VBN yielded) (NP (PDT such) (DT a) (JJ flat) (, ,) (VBG plodding) (NN picture))))))
(ROOT (VP (MD ) (VP (VB ) (VP (VBN ) (NP (PDT ) (DT ) (JJ ) (, ) (VBG ) (NN ))))))