instruction: Is the next sentence syntactically and semantically acceptable?

The snake flattened itself against the rock.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Who did Kim work for and Sandy rely on Mary?

response: unacceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Why did you say that you were leaving?

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

John will have been eating cake.

response:
acceptable