What ______ the number of the students in your school–About two thousand. A number of them _____ from the countryside.

In China, the number of cities is increasing _____ development is recognized across the world.

Are you ready to leave? —Almost, I’ll be ready to go just as soon as I putting the clean dishes away.

Here is such a difficult text _____ none of us can understand.Here is such a difficult text _____ none of us can understand it.

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