Obviously, I could not say much.
( Obviously ( , ( I ( ( ( could not ) ( say much ) ) . ) ) ) )
(ROOT (S (ADVP (RB Obviously)) (, ,) (NP (PRP I)) (VP (MD could) (RB not) (VP (VB say) (NP (RB much)))) (. .)))
I didn't say much.
( I ( ( ( did n't ) ( say much ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBD did) (RB n't) (VP (VB say) (NP (RB much)))) (. .)))