The new online library makes       possible for students to choose books by smart phone off campus．

We teachers must see to ________that every student can understand.

Many people complained about the stones scattering on a roadway, but ______ did anything about getting the stone out of the way.

Put it down, Tom. You mustn’t read _________ letter.

May I have a talk with you , sir ? I have ______important to tell you.