You're given a sentence and your task is to classify whether the sentence is acceptable or not. Any sentence which is grammatically correct, has a naturalistic text, is written by a native speaker and which minimizes superfluous content is acceptable, otherwise unacceptable. If the sentence is acceptable then write "acceptable", otherwise "unacceptable".

[Q]: Willy is taller than that Bill is is generally believed.
[A]: unacceptable


[Q]: While Doc might claim that Bob had read his book, he won't the paper.
[A]: unacceptable


[Q]: He's the happiest that we ever talked to the boy who had seen him.
[A]:
unacceptable