instruction: Is the next sentence syntactically and semantically acceptable?

Brian wiped the fingerprints from under the cupboard.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Mary won't have been eating cake, but John.

response: unacceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Bill floated down the river for hours.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

The mouse nibbled on the cheese.

response:
acceptable