According to the school rules, no child _______ be allowed out of the school during the day, unless accompanied by an adult．

I can’t find my English book. I must ___ it at home this morning.

To be on the safe side, we should fill up the tank now, because we ______ run out of gas on the way.

—Could I use your bike?　—Yes, surely you ______.

 You can’t imagine that a well-behaved gentleman ______ be so rude to a lady.