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]: The problem knows easily.
[A]: unacceptable


[Q]: In the book, he talks about his ups and downs at school.
[A]: acceptable


[Q]: I've never seen a taller man than my father.
[A]:
acceptable