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".

One of the problems was the robins.
acceptable

Heidi believes Bill's description of herself.
unacceptable

Runaway cats spot easily.

unacceptable