. Leave your key with a neighbor __________ you lock yourself out one day.

I wondered if the man was our new headmaster but quickly______the thought， because he was too young．

But for your timely warning, we _____ into great trouble.— Well, you know we’re friends.

__________ do you have an Art Festival in your school —- Once a year.

________ is often the case with human beings, many animals sleep a lot when young, but sleep much less when they get older.