TASK DEFINITION: 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".
PROBLEM: Robert knows it is essential that he is well behaved.

SOLUTION: acceptable

PROBLEM: Janet broke at the vase.

SOLUTION: unacceptable

PROBLEM: Mary has more friends than two.

SOLUTION:
acceptable