Q: In this task, you're shown a three-part story, with a beginning, middle, and ending. Your job is to slightly modify the middle part, so that the whole story becomes unlikely, improbable, or inconsistent. Generated sentences must minimally alter the given middle, with at most 4 new words added/existing words removed. Your sentence should be grammatically and syntactically correct. Also stick to the context of the given story. For example, if the story talks about "doctors", you can talk about "health" or "diagnosis", but don't mention "aliens". Avoid introducing any extra/irrelevant information, and use names instead of pronouns (e.g. he / she) wherever possible. Avoid simply negating the original middle, for example:  "She likes cakes." is changed to "She doesn't like cakes."
Beginning: Mary's cat keeps grooming her nails on the couch. Middle: The nails was sharp enough to notice the damage. Ending: Her cat rips out a section of the couch while grooming its claws.
A:
The knife was sharp enough to cut a shoe.