a dull girl , that 's all 
(ROOT (S (S (NP (DT a) (JJ dull) (NN girl))) (, ,) (NP (DT that)) (VP (VBZ 's) (ADVP (RB all)))))
(ROOT (S (S (NP (DT ) (JJ ) (NN ))) (, ) (NP (DT )) (VP (VBZ ) (ADVP (RB )))))