Oh! I came in a hurry and forgot to bring food.— It doesn’t matter, You can have______

If (如果) he isn’t at school. Please call me _______ 453-7868. [ ]

Peter doesn’t tell me when he _______. I’ll telephone you as soon as he ______.

I had _________ entered the classroom when I noticed the headmaster was sitting at the back.

Mike, please be quiet, or the other students hear me clearly.