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: Sandy sang a song for me.

A: acceptable
****
Q: John believed it.

A: acceptable
****
Q: John referred from the building.

A:
unacceptable
****