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".
--------
Question: Robert knows it is essential that he is well behaved.

Answer: acceptable


Question: The stone knocked against the pole into the road.

Answer: acceptable


Question: This should be the beginning of a beautiful friendship.

Answer:
acceptable