227. It is necessary that the question_______ at once.

Tom didn’t go hiking with his classmates ____ his illness.

It was amazing that the army _______ its homeland against all enemies.

It didn’t take long for them to ______ the cheat,who pretended to be an expert in this field. [ ]

I think students should have mobile phones to call their parents.—_____. They often use them to play games instead.