The number of teachers in our college _____ greatly increased this term. A number of teachers in this school _____ from the countryside.

—How much are the two pairs of shoes?  —They are not expensive. I think fifty dollars ______ enough.

The poor ______ living in the mountain ____ top is covered with green trees.

I took mathematics and physics because I think that ________ very important for me to make further research in this field.

Either you or one of your students _______to attend the meeting that will be held tomorrow.