30. —This wall of air is an effective answer to the problem and it ______ work. —But it is a question to put such a wall of air around the statue.
John was ill. Have you heard about ____?
____ could do such thing?
How long ____ she would stay here?
Your performance in the driving test didn’t reach the required standard — ____, you failed.
---- Have you fed the dog? ---- No, but ____.