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]: It is this hat that it is certain that he was wearing.
[A]: acceptable


[Q]: We proved conclusively Smith to be the thief.
[A]: unacceptable


[Q]: John is prouder of having gone than John expected me to believe that he wasn't.
[A]:
unacceptable