instruction: Is the next sentence syntactically and semantically acceptable?

They surrounded.

response: unacceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Alex read the newspaper for an hour.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

Bill believes Anna and him to be similar.

response: acceptable

instruction: Is the next sentence syntactically and semantically acceptable?

He is believed to have been at the game.

response:
acceptable