The number of people invited_____40, but a number of them______absent for different reasons.

—What _______ the number of the students in your school?—About two thousand. A number of them _______ from the countryside.

Mom,         my friends, Dave and Jack.

Either you or one of your students _______ to attend the meeting that is due tomorrow. 

The university estimates that living expenses for international students________around $8,450 a year，which________a burden for some of them.                     (2013·湖南，33)