TASK DEFINITION: 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".
PROBLEM: John suddenly got off the bus.

SOLUTION: acceptable

PROBLEM: Nixon's behavior gave an idea for a book to every journalist living in New York.

SOLUTION: acceptable

PROBLEM: John hasn't been singing a song.

SOLUTION:
acceptable