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: Copper rods bend easily.

A: acceptable
****
Q: How do you wonder whether John said that Mary solved the problem?

A: unacceptable
****
Q: The travelers have returned from their vacation.

A:
acceptable
****