Her voice was doubtful.
( ( Her voice ) ( ( was doubtful ) . ) )
(ROOT (S (NP (PRP$ Her) (NN voice)) (VP (VBD was) (ADJP (JJ doubtful))) (. .)))
She sounded doubtful about it.
( She ( ( ( sounded doubtful ) ( about it ) ) . ) )
(ROOT (S (NP (PRP She)) (VP (VBD sounded) (ADJP (JJ doubtful)) (PP (IN about) (NP (PRP it)))) (. .)))