instruction: Is the next sentence syntactically and semantically acceptable?

The book of poems with a red cover from Blackwell by Robert Burns takes a very long time to read.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

It is rumored that he is on his way out.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

She made light, not too surprisingly, of the difficulties we might have at the border.

response: unacceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Who seemed to have left first?

response:
acceptable