—Excuse me, what’s this for?—It’s a cleaner and it       to pick up dirt.

   —Mary was heard_______ just now. What happened?—John was telling a joke.

The television ________. It doesn’t work now.

–Our classroom _________ twice a day. So it is very clean.–It is important for us to do this.

We know that about seventy percent _____ the earth _____ covered by water.