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".

A is similar to B.
acceptable

Whether this is feasible hasn't yet been determined.
acceptable

I had hoped that it was true that Rosa Luxemburg had actually defected to Iceland for many years.

acceptable