When he walked _______ my desk, he knocked my books _______ the floor.

Time is limited. I have to finish this tonight.—But it’s midnight now and you should have a sleep ______ much work you have to do.

annual International Volunteers Day, the world _____ the work of millions of people who give their time to help others.

It remains to be seen________North Korea willremain stable under its new young leader

E-mail, as well as telephones, ______ an importantpart in daily communication.