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".

Suddenly an ugly old man entered the hall.
acceptable

Willy is taller than that Bill is is generally believed.
unacceptable

John placed on the table.

unacceptable