_____ at the door before you come into the room.

 — How can I prepare for class, Mr. Johnson?　　　　— __you ____ my web page? You can download the notes and read them ahead of time.

It’s the third time ________ late for school this week. 

Mary couldn’t make herself _______ attention to because her classmates made so much noise.

Air is to us _____ water is to fish.