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".

How much harder has it rained, when you see a faster flow in the river?
acceptable

John can to kick the ball.
unacceptable

It is believed to be obvious by everyone that Fred is crazy.

acceptable